cc/scheduler/scheduler_state_machine.cc

   1 // Copyright 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "cc/scheduler/scheduler_state_machine.h"
   6
   7 #include "base/format_macros.h"
   8 #include "base/logging.h"
   9 #include "base/strings/stringprintf.h"
  10 #include "base/trace_event/trace_event.h"
  11 #include "base/trace_event/trace_event_argument.h"
  12 #include "base/values.h"
  13 #include "ui/gfx/frame_time.h"
  14
  15 namespace cc {
  16
  17 SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
  18     : settings_(settings),
  19       output_surface_state_(OUTPUT_SURFACE_LOST),
  20       begin_impl_frame_state_(BEGIN_IMPL_FRAME_STATE_IDLE),
  21       commit_state_(COMMIT_STATE_IDLE),
  22       forced_redraw_state_(FORCED_REDRAW_STATE_IDLE),
  23       commit_count_(0),
  24       current_frame_number_(0),
  25       last_frame_number_animate_performed_(-1),
  26       last_frame_number_swap_performed_(-1),
  27       last_frame_number_swap_requested_(-1),
  28       last_frame_number_begin_main_frame_sent_(-1),
  29       last_frame_number_invalidate_output_surface_performed_(-1),
  30       animate_funnel_(false),
  31       request_swap_funnel_(false),
  32       send_begin_main_frame_funnel_(false),
  33       invalidate_output_surface_funnel_(false),
  34       prepare_tiles_funnel_(0),
  35       consecutive_checkerboard_animations_(0),
  36       max_pending_swaps_(1),
  37       pending_swaps_(0),
  38       needs_redraw_(false),
  39       needs_animate_(false),
  40       needs_prepare_tiles_(false),
  41       needs_commit_(false),
  42       visible_(false),
  43       can_start_(false),
  44       can_draw_(false),
  45       has_pending_tree_(false),
  46       pending_tree_is_ready_for_activation_(false),
  47       active_tree_needs_first_draw_(false),
  48       did_create_and_initialize_first_output_surface_(false),
  49       impl_latency_takes_priority_(false),
  50       skip_next_begin_main_frame_to_reduce_latency_(false),
  51       skip_begin_main_frame_to_reduce_latency_(false),
  52       continuous_painting_(false),
  53       children_need_begin_frames_(false),
  54       defer_commits_(false),
  55       video_needs_begin_frames_(false),
  56       last_commit_had_no_updates_(false),
  57       wait_for_active_tree_ready_to_draw_(false),
  58       did_request_swap_in_last_frame_(false),
  59       did_perform_swap_in_last_draw_(false) {
  60 }
  61
  62 const char* SchedulerStateMachine::OutputSurfaceStateToString(
  63     OutputSurfaceState state) {
  64   switch (state) {
  65     case OUTPUT_SURFACE_ACTIVE:
  66       return "OUTPUT_SURFACE_ACTIVE";
  67     case OUTPUT_SURFACE_LOST:
  68       return "OUTPUT_SURFACE_LOST";
  69     case OUTPUT_SURFACE_CREATING:
  70       return "OUTPUT_SURFACE_CREATING";
  71     case OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT:
  72       return "OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT";
  73     case OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION:
  74       return "OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION";
  75   }
  76   NOTREACHED();
  77   return "???";
  78 }
  79
  80 const char* SchedulerStateMachine::BeginImplFrameStateToString(
  81     BeginImplFrameState state) {
  82   switch (state) {
  83     case BEGIN_IMPL_FRAME_STATE_IDLE:
  84       return "BEGIN_IMPL_FRAME_STATE_IDLE";
  85     case BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING:
  86       return "BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING";
  87     case BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME:
  88       return "BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME";
  89     case BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE:
  90       return "BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE";
  91   }
  92   NOTREACHED();
  93   return "???";
  94 }
  95
  96 const char* SchedulerStateMachine::BeginImplFrameDeadlineModeToString(
  97     BeginImplFrameDeadlineMode mode) {
  98   switch (mode) {
  99     case BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE:
 100       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE";
 101     case BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE:
 102       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE";
 103     case BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR:
 104       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR";
 105     case BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE:
 106       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE";
 107     case BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW:
 108       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW";
 109   }
 110   NOTREACHED();
 111   return "???";
 112 }
 113
 114 const char* SchedulerStateMachine::CommitStateToString(CommitState state) {
 115   switch (state) {
 116     case COMMIT_STATE_IDLE:
 117       return "COMMIT_STATE_IDLE";
 118     case COMMIT_STATE_BEGIN_MAIN_FRAME_SENT:
 119       return "COMMIT_STATE_BEGIN_MAIN_FRAME_SENT";
 120     case COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED:
 121       return "COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED";
 122     case COMMIT_STATE_READY_TO_COMMIT:
 123       return "COMMIT_STATE_READY_TO_COMMIT";
 124     case COMMIT_STATE_WAITING_FOR_ACTIVATION:
 125       return "COMMIT_STATE_WAITING_FOR_ACTIVATION";
 126     case COMMIT_STATE_WAITING_FOR_DRAW:
 127       return "COMMIT_STATE_WAITING_FOR_DRAW";
 128   }
 129   NOTREACHED();
 130   return "???";
 131 }
 132
 133 const char* SchedulerStateMachine::ForcedRedrawOnTimeoutStateToString(
 134     ForcedRedrawOnTimeoutState state) {
 135   switch (state) {
 136     case FORCED_REDRAW_STATE_IDLE:
 137       return "FORCED_REDRAW_STATE_IDLE";
 138     case FORCED_REDRAW_STATE_WAITING_FOR_COMMIT:
 139       return "FORCED_REDRAW_STATE_WAITING_FOR_COMMIT";
 140     case FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION:
 141       return "FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION";
 142     case FORCED_REDRAW_STATE_WAITING_FOR_DRAW:
 143       return "FORCED_REDRAW_STATE_WAITING_FOR_DRAW";
 144   }
 145   NOTREACHED();
 146   return "???";
 147 }
 148
 149 const char* SchedulerStateMachine::ActionToString(Action action) {
 150   switch (action) {
 151     case ACTION_NONE:
 152       return "ACTION_NONE";
 153     case ACTION_ANIMATE:
 154       return "ACTION_ANIMATE";
 155     case ACTION_SEND_BEGIN_MAIN_FRAME:
 156       return "ACTION_SEND_BEGIN_MAIN_FRAME";
 157     case ACTION_COMMIT:
 158       return "ACTION_COMMIT";
 159     case ACTION_ACTIVATE_SYNC_TREE:
 160       return "ACTION_ACTIVATE_SYNC_TREE";
 161     case ACTION_DRAW_AND_SWAP_IF_POSSIBLE:
 162       return "ACTION_DRAW_AND_SWAP_IF_POSSIBLE";
 163     case ACTION_DRAW_AND_SWAP_FORCED:
 164       return "ACTION_DRAW_AND_SWAP_FORCED";
 165     case ACTION_DRAW_AND_SWAP_ABORT:
 166       return "ACTION_DRAW_AND_SWAP_ABORT";
 167     case ACTION_BEGIN_OUTPUT_SURFACE_CREATION:
 168       return "ACTION_BEGIN_OUTPUT_SURFACE_CREATION";
 169     case ACTION_PREPARE_TILES:
 170       return "ACTION_PREPARE_TILES";
 171     case ACTION_INVALIDATE_OUTPUT_SURFACE:
 172       return "ACTION_INVALIDATE_OUTPUT_SURFACE";
 173   }
 174   NOTREACHED();
 175   return "???";
 176 }
 177
 178 scoped_refptr<base::trace_event::ConvertableToTraceFormat>
 179 SchedulerStateMachine::AsValue() const {
 180   scoped_refptr<base::trace_event::TracedValue> state =
 181       new base::trace_event::TracedValue();
 182   AsValueInto(state.get());
 183   return state;
 184 }
 185
 186 void SchedulerStateMachine::AsValueInto(
 187     base::trace_event::TracedValue* state) const {
 188   state->BeginDictionary("major_state");
 189   state->SetString("next_action", ActionToString(NextAction()));
 190   state->SetString("begin_impl_frame_state",
 191                    BeginImplFrameStateToString(begin_impl_frame_state_));
 192   state->SetString("commit_state", CommitStateToString(commit_state_));
 193   state->SetString("output_surface_state_",
 194                    OutputSurfaceStateToString(output_surface_state_));
 195   state->SetString("forced_redraw_state",
 196                    ForcedRedrawOnTimeoutStateToString(forced_redraw_state_));
 197   state->EndDictionary();
 198
 199   state->BeginDictionary("minor_state");
 200   state->SetInteger("commit_count", commit_count_);
 201   state->SetInteger("current_frame_number", current_frame_number_);
 202   state->SetInteger("last_frame_number_animate_performed",
 203                     last_frame_number_animate_performed_);
 204   state->SetInteger("last_frame_number_swap_performed",
 205                     last_frame_number_swap_performed_);
 206   state->SetInteger("last_frame_number_swap_requested",
 207                     last_frame_number_swap_requested_);
 208   state->SetInteger("last_frame_number_begin_main_frame_sent",
 209                     last_frame_number_begin_main_frame_sent_);
 210   state->SetBoolean("funnel: animate_funnel", animate_funnel_);
 211   state->SetBoolean("funnel: request_swap_funnel", request_swap_funnel_);
 212   state->SetBoolean("funnel: send_begin_main_frame_funnel",
 213                     send_begin_main_frame_funnel_);
 214   state->SetInteger("funnel: prepare_tiles_funnel", prepare_tiles_funnel_);
 215   state->SetBoolean("funnel: invalidate_output_surface_funnel",
 216                     invalidate_output_surface_funnel_);
 217   state->SetInteger("consecutive_checkerboard_animations",
 218                     consecutive_checkerboard_animations_);
 219   state->SetInteger("max_pending_swaps_", max_pending_swaps_);
 220   state->SetInteger("pending_swaps_", pending_swaps_);
 221   state->SetBoolean("needs_redraw", needs_redraw_);
 222   state->SetBoolean("needs_animate_", needs_animate_);
 223   state->SetBoolean("needs_prepare_tiles", needs_prepare_tiles_);
 224   state->SetBoolean("needs_commit", needs_commit_);
 225   state->SetBoolean("visible", visible_);
 226   state->SetBoolean("can_start", can_start_);
 227   state->SetBoolean("can_draw", can_draw_);
 228   state->SetBoolean("has_pending_tree", has_pending_tree_);
 229   state->SetBoolean("pending_tree_is_ready_for_activation",
 230                     pending_tree_is_ready_for_activation_);
 231   state->SetBoolean("active_tree_needs_first_draw",
 232                     active_tree_needs_first_draw_);
 233   state->SetBoolean("wait_for_active_tree_ready_to_draw",
 234                     wait_for_active_tree_ready_to_draw_);
 235   state->SetBoolean("did_create_and_initialize_first_output_surface",
 236                     did_create_and_initialize_first_output_surface_);
 237   state->SetBoolean("impl_latency_takes_priority",
 238                     impl_latency_takes_priority_);
 239   state->SetBoolean("main_thread_is_in_high_latency_mode",
 240                     MainThreadIsInHighLatencyMode());
 241   state->SetBoolean("skip_begin_main_frame_to_reduce_latency",
 242                     skip_begin_main_frame_to_reduce_latency_);
 243   state->SetBoolean("skip_next_begin_main_frame_to_reduce_latency",
 244                     skip_next_begin_main_frame_to_reduce_latency_);
 245   state->SetBoolean("continuous_painting", continuous_painting_);
 246   state->SetBoolean("children_need_begin_frames", children_need_begin_frames_);
 247   state->SetBoolean("video_needs_begin_frames", video_needs_begin_frames_);
 248   state->SetBoolean("defer_commits", defer_commits_);
 249   state->SetBoolean("last_commit_had_no_updates", last_commit_had_no_updates_);
 250   state->SetBoolean("did_request_swap_in_last_frame",
 251                     did_request_swap_in_last_frame_);
 252   state->SetBoolean("did_perform_swap_in_last_draw",
 253                     did_perform_swap_in_last_draw_);
 254   state->EndDictionary();
 255 }
 256
 257 bool SchedulerStateMachine::PendingDrawsShouldBeAborted() const {
 258   // These are all the cases where we normally cannot or do not want to draw
 259   // but, if needs_redraw_ is true and we do not draw to make forward progress,
 260   // we might deadlock with the main thread.
 261   // This should be a superset of PendingActivationsShouldBeForced() since
 262   // activation of the pending tree is blocked by drawing of the active tree and
 263   // the main thread might be blocked on activation of the most recent commit.
 264   if (PendingActivationsShouldBeForced())
 265     return true;
 266
 267   // Additional states where we should abort draws.
 268   if (!can_draw_)
 269     return true;
 270   return false;
 271 }
 272
 273 bool SchedulerStateMachine::PendingActivationsShouldBeForced() const {
 274   // There is no output surface to trigger our activations.
 275   // If we do not force activations to make forward progress, we might deadlock
 276   // with the main thread.
 277   if (output_surface_state_ == OUTPUT_SURFACE_LOST)
 278     return true;
 279
 280   // If we're not visible, we should force activation.
 281   // Since we set RequiresHighResToDraw when becoming visible, we ensure that we
 282   // don't checkerboard until all visible resources are done. Furthermore, if we
 283   // do keep the pending tree around, when becoming visible we might activate
 284   // prematurely causing RequiresHighResToDraw flag to be reset. In all cases,
 285   // we can simply activate on becoming invisible since we don't need to draw
 286   // the active tree when we're in this state.
 287   if (!visible_)
 288     return true;
 289
 290   return false;
 291 }
 292
 293 bool SchedulerStateMachine::ShouldBeginOutputSurfaceCreation() const {
 294   // Don't try to initialize too early.
 295   if (!can_start_)
 296     return false;
 297
 298   // We only want to start output surface initialization after the
 299   // previous commit is complete.
 300   if (commit_state_ != COMMIT_STATE_IDLE)
 301     return false;
 302
 303   // Make sure the BeginImplFrame from any previous OutputSurfaces
 304   // are complete before creating the new OutputSurface.
 305   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_IDLE)
 306     return false;
 307
 308   // We want to clear the pipeline of any pending draws and activations
 309   // before starting output surface initialization. This allows us to avoid
 310   // weird corner cases where we abort draws or force activation while we
 311   // are initializing the output surface.
 312   if (active_tree_needs_first_draw_ || has_pending_tree_)
 313     return false;
 314
 315   // We need to create the output surface if we don't have one and we haven't
 316   // started creating one yet.
 317   return output_surface_state_ == OUTPUT_SURFACE_LOST;
 318 }
 319
 320 bool SchedulerStateMachine::ShouldDraw() const {
 321   // If we need to abort draws, we should do so ASAP since the draw could
 322   // be blocking other important actions (like output surface initialization),
 323   // from occurring. If we are waiting for the first draw, then perform the
 324   // aborted draw to keep things moving. If we are not waiting for the first
 325   // draw however, we don't want to abort for no reason.
 326   if (PendingDrawsShouldBeAborted())
 327     return active_tree_needs_first_draw_;
 328
 329   // Do not draw too many times in a single frame. It's okay that we don't check
 330   // this before checking for aborted draws because aborted draws do not request
 331   // a swap.
 332   if (request_swap_funnel_)
 333     return false;
 334
 335   // Don't draw if we are waiting on the first commit after a surface.
 336   if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE)
 337     return false;
 338
 339   // Do not queue too many swaps.
 340   if (pending_swaps_ >= max_pending_swaps_)
 341     return false;
 342
 343   // Except for the cases above, do not draw outside of the BeginImplFrame
 344   // deadline.
 345   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
 346     return false;
 347
 348   // Only handle forced redraws due to timeouts on the regular deadline.
 349   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
 350     return true;
 351
 352   return needs_redraw_;
 353 }
 354
 355 bool SchedulerStateMachine::ShouldActivatePendingTree() const {
 356   // There is nothing to activate.
 357   if (!has_pending_tree_)
 358     return false;
 359
 360   // We should not activate a second tree before drawing the first one.
 361   // Even if we need to force activation of the pending tree, we should abort
 362   // drawing the active tree first.
 363   if (active_tree_needs_first_draw_)
 364     return false;
 365
 366   // If we want to force activation, do so ASAP.
 367   if (PendingActivationsShouldBeForced())
 368     return true;
 369
 370   // At this point, only activate if we are ready to activate.
 371   return pending_tree_is_ready_for_activation_;
 372 }
 373
 374 bool SchedulerStateMachine::ShouldAnimate() const {
 375   // Do not animate too many times in a single frame.
 376   if (animate_funnel_)
 377     return false;
 378
 379   // Don't animate if we are waiting on the first commit after a surface.
 380   if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE)
 381     return false;
 382
 383   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING &&
 384       begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
 385     return false;
 386
 387   return needs_redraw_ || needs_animate_;
 388 }
 389
 390 bool SchedulerStateMachine::CouldSendBeginMainFrame() const {
 391   if (!needs_commit_)
 392     return false;
 393
 394   // We can not perform commits if we are not visible.
 395   if (!visible_)
 396     return false;
 397
 398   // Do not make a new commits when it is deferred.
 399   if (defer_commits_)
 400     return false;
 401
 402   return true;
 403 }
 404
 405 bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
 406   if (!CouldSendBeginMainFrame())
 407     return false;
 408
 409   // Do not send begin main frame too many times in a single frame.
 410   if (send_begin_main_frame_funnel_)
 411     return false;
 412
 413   // Only send BeginMainFrame when there isn't another commit pending already.
 414   if (commit_state_ != COMMIT_STATE_IDLE)
 415     return false;
 416
 417   // Don't send BeginMainFrame early if we are prioritizing the active tree
 418   // because of impl_latency_takes_priority_.
 419   if (impl_latency_takes_priority_ &&
 420       (has_pending_tree_ || active_tree_needs_first_draw_)) {
 421     return false;
 422   }
 423
 424   // We should not send BeginMainFrame while we are in
 425   // BEGIN_IMPL_FRAME_STATE_IDLE since we might have new
 426   // user input arriving soon.
 427   // TODO(brianderson): Allow sending BeginMainFrame while idle when the main
 428   // thread isn't consuming user input.
 429   if (begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_IDLE &&
 430       BeginFrameNeeded())
 431     return false;
 432
 433   // We need a new commit for the forced redraw. This honors the
 434   // single commit per interval because the result will be swapped to screen.
 435   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT)
 436     return true;
 437
 438   // We shouldn't normally accept commits if there isn't an OutputSurface.
 439   if (!HasInitializedOutputSurface())
 440     return false;
 441
 442   // SwapAck throttle the BeginMainFrames unless we just swapped.
 443   // TODO(brianderson): Remove this restriction to improve throughput.
 444   bool just_swapped_in_deadline =
 445       begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE &&
 446       did_perform_swap_in_last_draw_;
 447   if (pending_swaps_ >= max_pending_swaps_ && !just_swapped_in_deadline)
 448     return false;
 449
 450   if (skip_begin_main_frame_to_reduce_latency_)
 451     return false;
 452
 453   return true;
 454 }
 455
 456 bool SchedulerStateMachine::ShouldCommit() const {
 457   if (commit_state_ != COMMIT_STATE_READY_TO_COMMIT)
 458     return false;
 459
 460   // We must not finish the commit until the pending tree is free.
 461   if (has_pending_tree_) {
 462     DCHECK(settings_.main_frame_before_activation_enabled);
 463     return false;
 464   }
 465
 466   // Prioritize drawing the previous commit before finishing the next commit.
 467   if (active_tree_needs_first_draw_)
 468     return false;
 469
 470   return true;
 471 }
 472
 473 bool SchedulerStateMachine::ShouldPrepareTiles() const {
 474   // PrepareTiles only really needs to be called immediately after commit
 475   // and then periodically after that. Use a funnel to make sure we average
 476   // one PrepareTiles per BeginImplFrame in the long run.
 477   if (prepare_tiles_funnel_ > 0)
 478     return false;
 479
 480   // Limiting to once per-frame is not enough, since we only want to
 481   // prepare tiles _after_ draws.
 482   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
 483     return false;
 484
 485   return needs_prepare_tiles_;
 486 }
 487
 488 bool SchedulerStateMachine::ShouldInvalidateOutputSurface() const {
 489   // Do not invalidate too many times in a frame.
 490   if (invalidate_output_surface_funnel_)
 491     return false;
 492
 493   // Only the synchronous compositor requires invalidations.
 494   if (!settings_.using_synchronous_renderer_compositor)
 495     return false;
 496
 497   // Invalidations are only performed inside a BeginFrame.
 498   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING)
 499     return false;
 500
 501   // TODO(sunnyps): needs_prepare_tiles_ is needed here because PrepareTiles is
 502   // called only inside the deadline / draw phase. We could remove this if we
 503   // allowed PrepareTiles to happen in OnBeginImplFrame.
 504   return needs_redraw_ || needs_prepare_tiles_;
 505 }
 506
 507 SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
 508   if (ShouldActivatePendingTree())
 509     return ACTION_ACTIVATE_SYNC_TREE;
 510   if (ShouldCommit())
 511     return ACTION_COMMIT;
 512   if (ShouldAnimate())
 513     return ACTION_ANIMATE;
 514   if (ShouldDraw()) {
 515     if (PendingDrawsShouldBeAborted())
 516       return ACTION_DRAW_AND_SWAP_ABORT;
 517     else if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
 518       return ACTION_DRAW_AND_SWAP_FORCED;
 519     else
 520       return ACTION_DRAW_AND_SWAP_IF_POSSIBLE;
 521   }
 522   if (ShouldPrepareTiles())
 523     return ACTION_PREPARE_TILES;
 524   if (ShouldSendBeginMainFrame())
 525     return ACTION_SEND_BEGIN_MAIN_FRAME;
 526   if (ShouldInvalidateOutputSurface())
 527     return ACTION_INVALIDATE_OUTPUT_SURFACE;
 528   if (ShouldBeginOutputSurfaceCreation())
 529     return ACTION_BEGIN_OUTPUT_SURFACE_CREATION;
 530   return ACTION_NONE;
 531 }
 532
 533 void SchedulerStateMachine::UpdateState(Action action) {
 534   switch (action) {
 535     case ACTION_NONE:
 536       return;
 537
 538     case ACTION_ACTIVATE_SYNC_TREE:
 539       UpdateStateOnActivation();
 540       return;
 541
 542     case ACTION_ANIMATE:
 543       UpdateStateOnAnimate();
 544       return;
 545
 546     case ACTION_SEND_BEGIN_MAIN_FRAME:
 547       UpdateStateOnSendBeginMainFrame();
 548       return;
 549
 550     case ACTION_COMMIT: {
 551       bool commit_has_no_updates = false;
 552       UpdateStateOnCommit(commit_has_no_updates);
 553       return;
 554     }
 555
 556     case ACTION_DRAW_AND_SWAP_FORCED:
 557     case ACTION_DRAW_AND_SWAP_IF_POSSIBLE: {
 558       bool did_request_swap = true;
 559       UpdateStateOnDraw(did_request_swap);
 560       return;
 561     }
 562
 563     case ACTION_DRAW_AND_SWAP_ABORT: {
 564       bool did_request_swap = false;
 565       UpdateStateOnDraw(did_request_swap);
 566       return;
 567     }
 568
 569     case ACTION_BEGIN_OUTPUT_SURFACE_CREATION:
 570       UpdateStateOnBeginOutputSurfaceCreation();
 571       return;
 572
 573     case ACTION_PREPARE_TILES:
 574       UpdateStateOnPrepareTiles();
 575       return;
 576
 577     case ACTION_INVALIDATE_OUTPUT_SURFACE:
 578       UpdateStateOnInvalidateOutputSurface();
 579       return;
 580   }
 581 }
 582
 583 void SchedulerStateMachine::UpdateStateOnAnimate() {
 584   DCHECK(!animate_funnel_);
 585   last_frame_number_animate_performed_ = current_frame_number_;
 586   animate_funnel_ = true;
 587   needs_animate_ = false;
 588   // TODO(skyostil): Instead of assuming this, require the client to tell us.
 589   SetNeedsRedraw();
 590 }
 591
 592 void SchedulerStateMachine::UpdateStateOnSendBeginMainFrame() {
 593   DCHECK(!has_pending_tree_ || settings_.main_frame_before_activation_enabled);
 594   DCHECK(visible_);
 595   DCHECK(!send_begin_main_frame_funnel_);
 596   commit_state_ = COMMIT_STATE_BEGIN_MAIN_FRAME_SENT;
 597   needs_commit_ = false;
 598   send_begin_main_frame_funnel_ = true;
 599   last_frame_number_begin_main_frame_sent_ = current_frame_number_;
 600 }
 601
 602 void SchedulerStateMachine::UpdateStateOnCommit(bool commit_has_no_updates) {
 603   commit_count_++;
 604
 605   // Animate after commit even if we've already animated.
 606   if (!commit_has_no_updates)
 607     animate_funnel_ = false;
 608
 609   if (commit_has_no_updates || settings_.main_frame_before_activation_enabled) {
 610     commit_state_ = COMMIT_STATE_IDLE;
 611   } else if (settings_.impl_side_painting) {
 612     commit_state_ = COMMIT_STATE_WAITING_FOR_ACTIVATION;
 613   } else {
 614     commit_state_ = settings_.main_thread_should_always_be_low_latency
 615                         ? COMMIT_STATE_WAITING_FOR_DRAW
 616                         : COMMIT_STATE_IDLE;
 617   }
 618
 619   // If we are impl-side-painting but the commit was aborted, then we behave
 620   // mostly as if we are not impl-side-painting since there is no pending tree.
 621   has_pending_tree_ = settings_.impl_side_painting && !commit_has_no_updates;
 622
 623   // Update state related to forced draws.
 624   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT) {
 625     forced_redraw_state_ = has_pending_tree_
 626                                ? FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION
 627                                : FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
 628   }
 629
 630   // Update the output surface state.
 631   DCHECK_NE(output_surface_state_, OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION);
 632   if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT) {
 633     if (has_pending_tree_) {
 634       output_surface_state_ = OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION;
 635     } else {
 636       output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
 637       needs_redraw_ = true;
 638     }
 639   }
 640
 641   // Update state if we have a new active tree to draw, or if the active tree
 642   // was unchanged but we need to do a forced draw.
 643   if (!has_pending_tree_ &&
 644       (!commit_has_no_updates ||
 645        forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)) {
 646     needs_redraw_ = true;
 647     active_tree_needs_first_draw_ = true;
 648   }
 649
 650   // This post-commit work is common to both completed and aborted commits.
 651   pending_tree_is_ready_for_activation_ = false;
 652
 653   if (continuous_painting_)
 654     needs_commit_ = true;
 655   last_commit_had_no_updates_ = commit_has_no_updates;
 656 }
 657
 658 void SchedulerStateMachine::UpdateStateOnActivation() {
 659   if (commit_state_ == COMMIT_STATE_WAITING_FOR_ACTIVATION) {
 660     commit_state_ = settings_.main_thread_should_always_be_low_latency
 661                         ? COMMIT_STATE_WAITING_FOR_DRAW
 662                         : COMMIT_STATE_IDLE;
 663   }
 664
 665   if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION)
 666     output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
 667
 668   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION)
 669     forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
 670
 671   has_pending_tree_ = false;
 672   pending_tree_is_ready_for_activation_ = false;
 673   active_tree_needs_first_draw_ = true;
 674   needs_redraw_ = true;
 675 }
 676
 677 void SchedulerStateMachine::UpdateStateOnDraw(bool did_request_swap) {
 678   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
 679     forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
 680
 681   if (commit_state_ == COMMIT_STATE_WAITING_FOR_DRAW)
 682     commit_state_ = COMMIT_STATE_IDLE;
 683
 684   needs_redraw_ = false;
 685   active_tree_needs_first_draw_ = false;
 686
 687   if (did_request_swap) {
 688     DCHECK(!request_swap_funnel_);
 689     request_swap_funnel_ = true;
 690     did_request_swap_in_last_frame_ = true;
 691     last_frame_number_swap_requested_ = current_frame_number_;
 692   }
 693 }
 694
 695 void SchedulerStateMachine::UpdateStateOnPrepareTiles() {
 696   needs_prepare_tiles_ = false;
 697 }
 698
 699 void SchedulerStateMachine::UpdateStateOnBeginOutputSurfaceCreation() {
 700   DCHECK_EQ(output_surface_state_, OUTPUT_SURFACE_LOST);
 701   output_surface_state_ = OUTPUT_SURFACE_CREATING;
 702
 703   // The following DCHECKs make sure we are in the proper quiescent state.
 704   // The pipeline should be flushed entirely before we start output
 705   // surface creation to avoid complicated corner cases.
 706   DCHECK_EQ(commit_state_, COMMIT_STATE_IDLE);
 707   DCHECK(!has_pending_tree_);
 708   DCHECK(!active_tree_needs_first_draw_);
 709 }
 710
 711 void SchedulerStateMachine::UpdateStateOnInvalidateOutputSurface() {
 712   DCHECK(!invalidate_output_surface_funnel_);
 713   invalidate_output_surface_funnel_ = true;
 714   last_frame_number_invalidate_output_surface_performed_ =
 715       current_frame_number_;
 716
 717   // The synchronous compositor makes no guarantees about a draw coming in after
 718   // an invalidate so clear any flags that would cause the compositor's pipeline
 719   // to stall.
 720   active_tree_needs_first_draw_ = false;  // blocks commit if true
 721 }
 722
 723 void SchedulerStateMachine::SetSkipNextBeginMainFrameToReduceLatency() {
 724   TRACE_EVENT_INSTANT0("cc",
 725                        "Scheduler: SkipNextBeginMainFrameToReduceLatency",
 726                        TRACE_EVENT_SCOPE_THREAD);
 727   skip_next_begin_main_frame_to_reduce_latency_ = true;
 728 }
 729
 730 bool SchedulerStateMachine::BeginFrameRequiredForChildren() const {
 731   return children_need_begin_frames_;
 732 }
 733 bool SchedulerStateMachine::BeginFrameNeededForVideo() const {
 734   return video_needs_begin_frames_;
 735 }
 736
 737 bool SchedulerStateMachine::BeginFrameNeeded() const {
 738   // We can't handle BeginFrames when output surface isn't initialized.
 739   // TODO(brianderson): Support output surface creation inside a BeginFrame.
 740   if (!HasInitializedOutputSurface())
 741     return false;
 742
 743   // If we are not visible, we don't need BeginFrame messages.
 744   if (!visible_)
 745     return false;
 746
 747   return (BeginFrameRequiredForAction() || BeginFrameRequiredForChildren() ||
 748           BeginFrameNeededForVideo() || ProactiveBeginFrameWanted());
 749 }
 750
 751 void SchedulerStateMachine::SetChildrenNeedBeginFrames(
 752     bool children_need_begin_frames) {
 753   children_need_begin_frames_ = children_need_begin_frames;
 754 }
 755
 756 void SchedulerStateMachine::SetVideoNeedsBeginFrames(
 757     bool video_needs_begin_frames) {
 758   video_needs_begin_frames_ = video_needs_begin_frames;
 759 }
 760
 761 void SchedulerStateMachine::SetDeferCommits(bool defer_commits) {
 762   defer_commits_ = defer_commits;
 763 }
 764
 765 // These are the cases where we require a BeginFrame message to make progress
 766 // on requested actions.
 767 bool SchedulerStateMachine::BeginFrameRequiredForAction() const {
 768   // The forced draw respects our normal draw scheduling, so we need to
 769   // request a BeginImplFrame for it.
 770   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
 771     return true;
 772
 773   return needs_animate_ || needs_redraw_ || (needs_commit_ && !defer_commits_);
 774 }
 775
 776 // These are cases where we are very likely want a BeginFrame message in the
 777 // near future. Proactively requesting the BeginImplFrame helps hide the round
 778 // trip latency of the SetNeedsBeginFrame request that has to go to the
 779 // Browser.
 780 // This includes things like drawing soon, but might not actually have a new
 781 // frame to draw when we receive the next BeginImplFrame.
 782 bool SchedulerStateMachine::ProactiveBeginFrameWanted() const {
 783   // Do not be proactive when invisible.
 784   if (!visible_)
 785     return false;
 786
 787   // We should proactively request a BeginImplFrame if a commit is pending
 788   // because we will want to draw if the commit completes quickly. Do not
 789   // request frames when commits are disabled, because the frame requests will
 790   // not provide the needed commit (and will wake up the process when it could
 791   // stay idle).
 792   if ((commit_state_ != COMMIT_STATE_IDLE) && !defer_commits_)
 793     return true;
 794
 795   // If the pending tree activates quickly, we'll want a BeginImplFrame soon
 796   // to draw the new active tree.
 797   if (has_pending_tree_)
 798     return true;
 799
 800   // Changing priorities may allow us to activate (given the new priorities),
 801   // which may result in a new frame.
 802   if (needs_prepare_tiles_)
 803     return true;
 804
 805   // If we just sent a swap request, it's likely that we are going to produce
 806   // another frame soon. This helps avoid negative glitches in our
 807   // SetNeedsBeginFrame requests, which may propagate to the BeginImplFrame
 808   // provider and get sampled at an inopportune time, delaying the next
 809   // BeginImplFrame.
 810   if (did_request_swap_in_last_frame_)
 811     return true;
 812
 813   // If the last commit was aborted because of early out (no updates), we should
 814   // still want a begin frame in case there is a commit coming again.
 815   if (last_commit_had_no_updates_)
 816     return true;
 817
 818   return false;
 819 }
 820
 821 void SchedulerStateMachine::OnBeginImplFrame() {
 822   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING;
 823   current_frame_number_++;
 824
 825   last_commit_had_no_updates_ = false;
 826   did_request_swap_in_last_frame_ = false;
 827
 828   // Clear funnels for any actions we perform during the frame.
 829   animate_funnel_ = false;
 830   send_begin_main_frame_funnel_ = false;
 831   invalidate_output_surface_funnel_ = false;
 832
 833   // "Drain" the PrepareTiles funnel.
 834   if (prepare_tiles_funnel_ > 0)
 835     prepare_tiles_funnel_--;
 836
 837   skip_begin_main_frame_to_reduce_latency_ =
 838       skip_next_begin_main_frame_to_reduce_latency_;
 839   skip_next_begin_main_frame_to_reduce_latency_ = false;
 840 }
 841
 842 void SchedulerStateMachine::OnBeginImplFrameDeadlinePending() {
 843   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME;
 844 }
 845
 846 void SchedulerStateMachine::OnBeginImplFrameDeadline() {
 847   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE;
 848
 849   did_perform_swap_in_last_draw_ = false;
 850
 851   // Clear funnels for any actions we perform during the deadline.
 852   request_swap_funnel_ = false;
 853 }
 854
 855 void SchedulerStateMachine::OnBeginImplFrameIdle() {
 856   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_IDLE;
 857 }
 858
 859 SchedulerStateMachine::BeginImplFrameDeadlineMode
 860 SchedulerStateMachine::CurrentBeginImplFrameDeadlineMode() const {
 861   if (settings_.using_synchronous_renderer_compositor) {
 862     // No deadline for synchronous compositor.
 863     return BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE;
 864   } else if (wait_for_active_tree_ready_to_draw_) {
 865     // When we are waiting for ready to draw signal, we do not wait to post a
 866     // deadline yet.
 867     return BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW;
 868   } else if (ShouldTriggerBeginImplFrameDeadlineImmediately()) {
 869     return BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE;
 870   } else if (needs_redraw_ && pending_swaps_ < max_pending_swaps_) {
 871     // We have an animation or fast input path on the impl thread that wants
 872     // to draw, so don't wait too long for a new active tree.
 873     // If we are swap throttled we should wait until we are unblocked.
 874     return BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR;
 875   } else {
 876     // The impl thread doesn't have anything it wants to draw and we are just
 877     // waiting for a new active tree or we are swap throttled. In short we are
 878     // blocked.
 879     return BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE;
 880   }
 881 }
 882
 883 bool SchedulerStateMachine::ShouldTriggerBeginImplFrameDeadlineImmediately()
 884     const {
 885   // TODO(brianderson): This should take into account multiple commit sources.
 886   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME)
 887     return false;
 888
 889   // If things are being aborted, end the current BeginImplFrame ASAP so we can
 890   // unblock creating the next output surface.
 891   if (PendingDrawsShouldBeAborted())
 892     return true;
 893
 894   // SwapAck throttle the deadline since we wont draw and swap anyway.
 895   if (pending_swaps_ >= max_pending_swaps_)
 896     return false;
 897
 898   if (active_tree_needs_first_draw_)
 899     return true;
 900
 901   if (!needs_redraw_)
 902     return false;
 903
 904   // This is used to prioritize impl-thread draws when the main thread isn't
 905   // producing anything, e.g., after an aborted commit. We also check that we
 906   // don't have a pending tree -- otherwise we should give it a chance to
 907   // activate.
 908   // TODO(skyostil): Revisit this when we have more accurate deadline estimates.
 909   if (commit_state_ == COMMIT_STATE_IDLE && !has_pending_tree_)
 910     return true;
 911
 912   // Prioritize impl-thread draws in impl_latency_takes_priority_ mode.
 913   if (impl_latency_takes_priority_)
 914     return true;
 915
 916   return false;
 917 }
 918
 919 bool SchedulerStateMachine::MainThreadIsInHighLatencyMode() const {
 920   // If a commit is pending before the previous commit has been drawn, we
 921   // are definitely in a high latency mode.
 922   if (CommitPending() && (active_tree_needs_first_draw_ || has_pending_tree_))
 923     return true;
 924
 925   // If we just sent a BeginMainFrame and haven't hit the deadline yet, the main
 926   // thread is in a low latency mode.
 927   if (send_begin_main_frame_funnel_ &&
 928       (begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING ||
 929        begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME))
 930     return false;
 931
 932   // If there's a commit in progress it must either be from the previous frame
 933   // or it started after the impl thread's deadline. In either case the main
 934   // thread is in high latency mode.
 935   if (CommitPending())
 936     return true;
 937
 938   // Similarly, if there's a pending tree the main thread is in high latency
 939   // mode, because either
 940   //   it's from the previous frame
 941   // or
 942   //   we're currently drawing the active tree and the pending tree will thus
 943   //   only be drawn in the next frame.
 944   if (has_pending_tree_)
 945     return true;
 946
 947   if (begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE) {
 948     // Even if there's a new active tree to draw at the deadline or we've just
 949     // swapped it, it may have been triggered by a previous BeginImplFrame, in
 950     // which case the main thread is in a high latency mode.
 951     return (active_tree_needs_first_draw_ || did_perform_swap_in_last_draw_) &&
 952            !send_begin_main_frame_funnel_;
 953   }
 954
 955   // If the active tree needs its first draw in any other state, we know the
 956   // main thread is in a high latency mode.
 957   return active_tree_needs_first_draw_;
 958 }
 959
 960 void SchedulerStateMachine::SetVisible(bool visible) { visible_ = visible; }
 961
 962 void SchedulerStateMachine::SetCanDraw(bool can_draw) { can_draw_ = can_draw; }
 963
 964 void SchedulerStateMachine::SetNeedsRedraw() { needs_redraw_ = true; }
 965
 966 void SchedulerStateMachine::SetNeedsAnimate() {
 967   needs_animate_ = true;
 968 }
 969
 970 void SchedulerStateMachine::SetWaitForReadyToDraw() {
 971   DCHECK(settings_.impl_side_painting);
 972   wait_for_active_tree_ready_to_draw_ = true;
 973 }
 974
 975 void SchedulerStateMachine::SetNeedsPrepareTiles() {
 976   if (!needs_prepare_tiles_) {
 977     TRACE_EVENT0("cc", "SchedulerStateMachine::SetNeedsPrepareTiles");
 978     needs_prepare_tiles_ = true;
 979   }
 980 }
 981
 982 void SchedulerStateMachine::SetMaxSwapsPending(int max) {
 983   max_pending_swaps_ = max;
 984 }
 985
 986 void SchedulerStateMachine::DidSwapBuffers() {
 987   pending_swaps_++;
 988   DCHECK_LE(pending_swaps_, max_pending_swaps_);
 989
 990   did_perform_swap_in_last_draw_ = true;
 991   last_frame_number_swap_performed_ = current_frame_number_;
 992 }
 993
 994 void SchedulerStateMachine::DidSwapBuffersComplete() {
 995   DCHECK_GT(pending_swaps_, 0);
 996   pending_swaps_--;
 997 }
 998
 999 void SchedulerStateMachine::SetImplLatencyTakesPriority(
1000     bool impl_latency_takes_priority) {
1001   impl_latency_takes_priority_ = impl_latency_takes_priority;
1002 }
1003
1004 void SchedulerStateMachine::DidDrawIfPossibleCompleted(DrawResult result) {
1005   switch (result) {
1006     case INVALID_RESULT:
1007       NOTREACHED() << "Uninitialized DrawResult.";
1008       break;
1009     case DRAW_ABORTED_CANT_DRAW:
1010     case DRAW_ABORTED_CONTEXT_LOST:
1011       NOTREACHED() << "Invalid return value from DrawAndSwapIfPossible:"
1012                    << result;
1013       break;
1014     case DRAW_SUCCESS:
1015       consecutive_checkerboard_animations_ = 0;
1016       forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
1017       break;
1018     case DRAW_ABORTED_CHECKERBOARD_ANIMATIONS:
1019       needs_redraw_ = true;
1020
1021       // If we're already in the middle of a redraw, we don't need to
1022       // restart it.
1023       if (forced_redraw_state_ != FORCED_REDRAW_STATE_IDLE)
1024         return;
1025
1026       needs_commit_ = true;
1027       consecutive_checkerboard_animations_++;
1028       if (settings_.timeout_and_draw_when_animation_checkerboards &&
1029           consecutive_checkerboard_animations_ >=
1030               settings_.maximum_number_of_failed_draws_before_draw_is_forced_) {
1031         consecutive_checkerboard_animations_ = 0;
1032         // We need to force a draw, but it doesn't make sense to do this until
1033         // we've committed and have new textures.
1034         forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_COMMIT;
1035       }
1036       break;
1037     case DRAW_ABORTED_MISSING_HIGH_RES_CONTENT:
1038       // It's not clear whether this missing content is because of missing
1039       // pictures (which requires a commit) or because of memory pressure
1040       // removing textures (which might not).  To be safe, request a commit
1041       // anyway.
1042       needs_commit_ = true;
1043       break;
1044   }
1045 }
1046
1047 void SchedulerStateMachine::SetNeedsCommit() {
1048   needs_commit_ = true;
1049 }
1050
1051 void SchedulerStateMachine::NotifyReadyToCommit() {
1052   DCHECK(commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED)
1053       << AsValue()->ToString();
1054   commit_state_ = COMMIT_STATE_READY_TO_COMMIT;
1055   // In main thread low latency mode, commit should happen right after
1056   // BeginFrame, meaning when this function is called, next action should be
1057   // commit.
1058   if (settings_.main_thread_should_always_be_low_latency)
1059     DCHECK(ShouldCommit());
1060 }
1061
1062 void SchedulerStateMachine::BeginMainFrameAborted(CommitEarlyOutReason reason) {
1063   DCHECK_EQ(commit_state_, COMMIT_STATE_BEGIN_MAIN_FRAME_SENT);
1064   switch (reason) {
1065     case CommitEarlyOutReason::ABORTED_OUTPUT_SURFACE_LOST:
1066     case CommitEarlyOutReason::ABORTED_NOT_VISIBLE:
1067     case CommitEarlyOutReason::ABORTED_DEFERRED_COMMIT:
1068       commit_state_ = COMMIT_STATE_IDLE;
1069       SetNeedsCommit();
1070       return;
1071     case CommitEarlyOutReason::FINISHED_NO_UPDATES:
1072       bool commit_has_no_updates = true;
1073       UpdateStateOnCommit(commit_has_no_updates);
1074       return;
1075   }
1076 }
1077
1078 void SchedulerStateMachine::DidPrepareTiles() {
1079   needs_prepare_tiles_ = false;
1080   // "Fill" the PrepareTiles funnel.
1081   prepare_tiles_funnel_++;
1082 }
1083
1084 void SchedulerStateMachine::DidLoseOutputSurface() {
1085   if (output_surface_state_ == OUTPUT_SURFACE_LOST ||
1086       output_surface_state_ == OUTPUT_SURFACE_CREATING)
1087     return;
1088   output_surface_state_ = OUTPUT_SURFACE_LOST;
1089   needs_redraw_ = false;
1090   wait_for_active_tree_ready_to_draw_ = false;
1091 }
1092
1093 void SchedulerStateMachine::NotifyReadyToActivate() {
1094   if (has_pending_tree_)
1095     pending_tree_is_ready_for_activation_ = true;
1096 }
1097
1098 void SchedulerStateMachine::NotifyReadyToDraw() {
1099   wait_for_active_tree_ready_to_draw_ = false;
1100 }
1101
1102 void SchedulerStateMachine::DidCreateAndInitializeOutputSurface() {
1103   DCHECK_EQ(output_surface_state_, OUTPUT_SURFACE_CREATING);
1104   output_surface_state_ = OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT;
1105
1106   if (did_create_and_initialize_first_output_surface_) {
1107     // TODO(boliu): See if we can remove this when impl-side painting is always
1108     // on. Does anything on the main thread need to update after recreate?
1109     needs_commit_ = true;
1110   }
1111   did_create_and_initialize_first_output_surface_ = true;
1112   pending_swaps_ = 0;
1113 }
1114
1115 void SchedulerStateMachine::NotifyBeginMainFrameStarted() {
1116   DCHECK_EQ(commit_state_, COMMIT_STATE_BEGIN_MAIN_FRAME_SENT);
1117   commit_state_ = COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED;
1118 }
1119
1120 bool SchedulerStateMachine::HasInitializedOutputSurface() const {
1121   switch (output_surface_state_) {
1122     case OUTPUT_SURFACE_LOST:
1123     case OUTPUT_SURFACE_CREATING:
1124       return false;
1125
1126     case OUTPUT_SURFACE_ACTIVE:
1127     case OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT:
1128     case OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION:
1129       return true;
1130   }
1131   NOTREACHED();
1132   return false;
1133 }
1134
1135 std::string SchedulerStateMachine::GetStatesForDebugging() const {
1136   return base::StringPrintf("%c %d %d %d %c %c %c %d %d",
1137       needs_commit_ ? 'T' : 'F',
1138       static_cast<int>(output_surface_state_),
1139       static_cast<int>(begin_impl_frame_state_),
1140       static_cast<int>(commit_state_),
1141       has_pending_tree_ ? 'T' : 'F',
1142       pending_tree_is_ready_for_activation_ ? 'T' : 'F',
1143       active_tree_needs_first_draw_ ? 'T' : 'F',
1144       max_pending_swaps_,
1145       pending_swaps_);
1146 }
1147
1148 }  // namespace cc