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
  14 namespace cc {
  15
  16 SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
  17     : settings_(settings),
  18       output_surface_state_(OUTPUT_SURFACE_LOST),
  19       begin_impl_frame_state_(BEGIN_IMPL_FRAME_STATE_IDLE),
  20       begin_main_frame_state_(BEGIN_MAIN_FRAME_STATE_IDLE),
  21       forced_redraw_state_(FORCED_REDRAW_STATE_IDLE),
  22       commit_count_(0),
  23       current_frame_number_(0),
  24       last_frame_number_animate_performed_(-1),
  25       last_frame_number_swap_performed_(-1),
  26       last_frame_number_swap_requested_(-1),
  27       last_frame_number_begin_main_frame_sent_(-1),
  28       last_frame_number_invalidate_output_surface_performed_(-1),
  29       animate_funnel_(false),
  30       request_swap_funnel_(false),
  31       send_begin_main_frame_funnel_(true),
  32       invalidate_output_surface_funnel_(false),
  33       prepare_tiles_funnel_(0),
  34       consecutive_checkerboard_animations_(0),
  35       max_pending_swaps_(1),
  36       pending_swaps_(0),
  37       swaps_with_current_output_surface_(0),
  38       needs_redraw_(false),
  39       needs_animate_(false),
  40       needs_prepare_tiles_(false),
  41       needs_begin_main_frame_(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       main_thread_missed_last_deadline_(false),
  51       skip_next_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_ready_to_draw_(false),
  58       did_request_swap_in_last_frame_(false),
  59       did_perform_swap_in_last_draw_(false) {}
  60
  61 const char* SchedulerStateMachine::OutputSurfaceStateToString(
  62     OutputSurfaceState state) {
  63   switch (state) {
  64     case OUTPUT_SURFACE_ACTIVE:
  65       return "OUTPUT_SURFACE_ACTIVE";
  66     case OUTPUT_SURFACE_LOST:
  67       return "OUTPUT_SURFACE_LOST";
  68     case OUTPUT_SURFACE_CREATING:
  69       return "OUTPUT_SURFACE_CREATING";
  70     case OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT:
  71       return "OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT";
  72     case OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION:
  73       return "OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION";
  74   }
  75   NOTREACHED();
  76   return "???";
  77 }
  78
  79 const char* SchedulerStateMachine::BeginImplFrameStateToString(
  80     BeginImplFrameState state) {
  81   switch (state) {
  82     case BEGIN_IMPL_FRAME_STATE_IDLE:
  83       return "BEGIN_IMPL_FRAME_STATE_IDLE";
  84     case BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING:
  85       return "BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING";
  86     case BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME:
  87       return "BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME";
  88     case BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE:
  89       return "BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE";
  90   }
  91   NOTREACHED();
  92   return "???";
  93 }
  94
  95 const char* SchedulerStateMachine::BeginImplFrameDeadlineModeToString(
  96     BeginImplFrameDeadlineMode mode) {
  97   switch (mode) {
  98     case BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE:
  99       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE";
 100     case BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE:
 101       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE";
 102     case BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR:
 103       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR";
 104     case BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE:
 105       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE";
 106     case BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW:
 107       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW";
 108   }
 109   NOTREACHED();
 110   return "???";
 111 }
 112
 113 const char* SchedulerStateMachine::BeginMainFrameStateToString(
 114     BeginMainFrameState state) {
 115   switch (state) {
 116     case BEGIN_MAIN_FRAME_STATE_IDLE:
 117       return "BEGIN_MAIN_FRAME_STATE_IDLE";
 118     case BEGIN_MAIN_FRAME_STATE_SENT:
 119       return "BEGIN_MAIN_FRAME_STATE_SENT";
 120     case BEGIN_MAIN_FRAME_STATE_STARTED:
 121       return "BEGIN_MAIN_FRAME_STATE_STARTED";
 122     case BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT:
 123       return "BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT";
 124     case BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION:
 125       return "BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION";
 126     case BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW:
 127       return "BEGIN_MAIN_FRAME_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("begin_main_frame_state",
 193                    BeginMainFrameStateToString(begin_main_frame_state_));
 194   state->SetString("output_surface_state_",
 195                    OutputSurfaceStateToString(output_surface_state_));
 196   state->SetString("forced_redraw_state",
 197                    ForcedRedrawOnTimeoutStateToString(forced_redraw_state_));
 198   state->EndDictionary();
 199
 200   state->BeginDictionary("minor_state");
 201   state->SetInteger("commit_count", commit_count_);
 202   state->SetInteger("current_frame_number", current_frame_number_);
 203   state->SetInteger("last_frame_number_animate_performed",
 204                     last_frame_number_animate_performed_);
 205   state->SetInteger("last_frame_number_swap_performed",
 206                     last_frame_number_swap_performed_);
 207   state->SetInteger("last_frame_number_swap_requested",
 208                     last_frame_number_swap_requested_);
 209   state->SetInteger("last_frame_number_begin_main_frame_sent",
 210                     last_frame_number_begin_main_frame_sent_);
 211   state->SetBoolean("funnel: animate_funnel", animate_funnel_);
 212   state->SetBoolean("funnel: request_swap_funnel", request_swap_funnel_);
 213   state->SetBoolean("funnel: send_begin_main_frame_funnel",
 214                     send_begin_main_frame_funnel_);
 215   state->SetInteger("funnel: prepare_tiles_funnel", prepare_tiles_funnel_);
 216   state->SetBoolean("funnel: invalidate_output_surface_funnel",
 217                     invalidate_output_surface_funnel_);
 218   state->SetInteger("consecutive_checkerboard_animations",
 219                     consecutive_checkerboard_animations_);
 220   state->SetInteger("max_pending_swaps_", max_pending_swaps_);
 221   state->SetInteger("pending_swaps_", pending_swaps_);
 222   state->SetInteger("swaps_with_current_output_surface",
 223                     swaps_with_current_output_surface_);
 224   state->SetBoolean("needs_redraw", needs_redraw_);
 225   state->SetBoolean("needs_animate_", needs_animate_);
 226   state->SetBoolean("needs_prepare_tiles", needs_prepare_tiles_);
 227   state->SetBoolean("needs_begin_main_frame", needs_begin_main_frame_);
 228   state->SetBoolean("visible", visible_);
 229   state->SetBoolean("can_start", can_start_);
 230   state->SetBoolean("can_draw", can_draw_);
 231   state->SetBoolean("has_pending_tree", has_pending_tree_);
 232   state->SetBoolean("pending_tree_is_ready_for_activation",
 233                     pending_tree_is_ready_for_activation_);
 234   state->SetBoolean("active_tree_needs_first_draw",
 235                     active_tree_needs_first_draw_);
 236   state->SetBoolean("wait_for_ready_to_draw", wait_for_ready_to_draw_);
 237   state->SetBoolean("did_create_and_initialize_first_output_surface",
 238                     did_create_and_initialize_first_output_surface_);
 239   state->SetBoolean("impl_latency_takes_priority",
 240                     impl_latency_takes_priority_);
 241   state->SetBoolean("main_thread_missed_last_deadline",
 242                     main_thread_missed_last_deadline_);
 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 (begin_main_frame_state_ != BEGIN_MAIN_FRAME_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 (SwapThrottled())
 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_begin_main_frame_)
 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::SendingBeginMainFrameMightCauseDeadlock() const {
 406   // NPAPI is the only case where the UI thread makes synchronous calls to the
 407   // Renderer main thread. During that synchronous call, we may not get a
 408   // SwapAck for the UI thread, which may prevent BeginMainFrame's from
 409   // completing if there's enough back pressure. If the BeginMainFrame can't
 410   // make progress, the Renderer can't service the UI thread's synchronous call
 411   // and we have deadlock.
 412   // This returns true if there's too much backpressure to finish a commit
 413   // if we were to initiate a BeginMainFrame.
 414   return has_pending_tree_ && active_tree_needs_first_draw_ && SwapThrottled();
 415 }
 416
 417 bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
 418   if (!CouldSendBeginMainFrame())
 419     return false;
 420
 421   // Do not send begin main frame too many times in a single frame or before
 422   // the first BeginFrame.
 423   if (send_begin_main_frame_funnel_)
 424     return false;
 425
 426   // Only send BeginMainFrame when there isn't another commit pending already.
 427   // Other parts of the state machine indirectly defer the BeginMainFrame
 428   // by transitioning to WAITING commit states rather than going
 429   // immediately to IDLE.
 430   if (begin_main_frame_state_ != BEGIN_MAIN_FRAME_STATE_IDLE)
 431     return false;
 432
 433   // Don't send BeginMainFrame early if we are prioritizing the active tree
 434   // because of impl_latency_takes_priority_.
 435   if (impl_latency_takes_priority_ &&
 436       (has_pending_tree_ || active_tree_needs_first_draw_)) {
 437     return false;
 438   }
 439
 440   // We should not send BeginMainFrame while we are in the idle state since we
 441   // might have new user input arriving soon. It's okay to send BeginMainFrame
 442   // for the synchronous compositor because the main thread is always high
 443   // latency in that case.
 444   // TODO(brianderson): Allow sending BeginMainFrame while idle when the main
 445   // thread isn't consuming user input for non-synchronous compositor.
 446   if (!settings_.using_synchronous_renderer_compositor &&
 447       begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_IDLE) {
 448     return false;
 449   }
 450
 451   // We need a new commit for the forced redraw. This honors the
 452   // single commit per interval because the result will be swapped to screen.
 453   // TODO(brianderson): Remove this or move it below the
 454   // SendingBeginMainFrameMightCauseDeadlock check since  we want to avoid
 455   // ever returning true from this method if we might cause deadlock.
 456   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT)
 457     return true;
 458
 459   // We shouldn't normally accept commits if there isn't an OutputSurface.
 460   if (!HasInitializedOutputSurface())
 461     return false;
 462
 463   // Make sure the BeginMainFrame can finish eventually if we start it.
 464   if (SendingBeginMainFrameMightCauseDeadlock())
 465     return false;
 466
 467   if (!settings_.main_frame_while_swap_throttled_enabled) {
 468     // SwapAck throttle the BeginMainFrames unless we just swapped to
 469     // potentially improve impl-thread latency over main-thread throughput.
 470     // TODO(brianderson): Remove this restriction to improve throughput or
 471     // make it conditional on impl_latency_takes_priority_.
 472     bool just_swapped_in_deadline =
 473         begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE &&
 474         did_perform_swap_in_last_draw_;
 475     if (SwapThrottled() && !just_swapped_in_deadline)
 476       return false;
 477   }
 478
 479   if (skip_next_begin_main_frame_to_reduce_latency_)
 480     return false;
 481
 482   return true;
 483 }
 484
 485 bool SchedulerStateMachine::ShouldCommit() const {
 486   if (begin_main_frame_state_ != BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT)
 487     return false;
 488
 489   // We must not finish the commit until the pending tree is free.
 490   if (has_pending_tree_) {
 491     DCHECK(settings_.main_frame_before_activation_enabled);
 492     return false;
 493   }
 494
 495   // If we only have an active tree, it is incorrect to replace it
 496   // before we've drawn it.
 497   DCHECK_IMPLIES(settings_.commit_to_active_tree,
 498                  !active_tree_needs_first_draw_);
 499
 500   return true;
 501 }
 502
 503 bool SchedulerStateMachine::ShouldPrepareTiles() const {
 504   // PrepareTiles only really needs to be called immediately after commit
 505   // and then periodically after that. Use a funnel to make sure we average
 506   // one PrepareTiles per BeginImplFrame in the long run.
 507   if (prepare_tiles_funnel_ > 0)
 508     return false;
 509
 510   // Limiting to once per-frame is not enough, since we only want to
 511   // prepare tiles _after_ draws.
 512   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
 513     return false;
 514
 515   return needs_prepare_tiles_;
 516 }
 517
 518 bool SchedulerStateMachine::ShouldInvalidateOutputSurface() const {
 519   // Do not invalidate too many times in a frame.
 520   if (invalidate_output_surface_funnel_)
 521     return false;
 522
 523   // Only the synchronous compositor requires invalidations.
 524   if (!settings_.using_synchronous_renderer_compositor)
 525     return false;
 526
 527   // Invalidations are only performed inside a BeginFrame.
 528   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING)
 529     return false;
 530
 531   // TODO(sunnyps): needs_prepare_tiles_ is needed here because PrepareTiles is
 532   // called only inside the deadline / draw phase. We could remove this if we
 533   // allowed PrepareTiles to happen in OnBeginImplFrame.
 534   return needs_redraw_ || needs_prepare_tiles_;
 535 }
 536
 537 SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
 538   if (ShouldActivatePendingTree())
 539     return ACTION_ACTIVATE_SYNC_TREE;
 540   if (ShouldCommit())
 541     return ACTION_COMMIT;
 542   if (ShouldAnimate())
 543     return ACTION_ANIMATE;
 544   if (ShouldDraw()) {
 545     if (PendingDrawsShouldBeAborted())
 546       return ACTION_DRAW_AND_SWAP_ABORT;
 547     else if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
 548       return ACTION_DRAW_AND_SWAP_FORCED;
 549     else
 550       return ACTION_DRAW_AND_SWAP_IF_POSSIBLE;
 551   }
 552   if (ShouldPrepareTiles())
 553     return ACTION_PREPARE_TILES;
 554   if (ShouldSendBeginMainFrame())
 555     return ACTION_SEND_BEGIN_MAIN_FRAME;
 556   if (ShouldInvalidateOutputSurface())
 557     return ACTION_INVALIDATE_OUTPUT_SURFACE;
 558   if (ShouldBeginOutputSurfaceCreation())
 559     return ACTION_BEGIN_OUTPUT_SURFACE_CREATION;
 560   return ACTION_NONE;
 561 }
 562
 563 void SchedulerStateMachine::WillAnimate() {
 564   DCHECK(!animate_funnel_);
 565   last_frame_number_animate_performed_ = current_frame_number_;
 566   animate_funnel_ = true;
 567   needs_animate_ = false;
 568   // TODO(skyostil): Instead of assuming this, require the client to tell us.
 569   SetNeedsRedraw();
 570 }
 571
 572 void SchedulerStateMachine::WillSendBeginMainFrame() {
 573   DCHECK(!has_pending_tree_ || settings_.main_frame_before_activation_enabled);
 574   DCHECK(visible_);
 575   DCHECK(!send_begin_main_frame_funnel_);
 576   begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_SENT;
 577   needs_begin_main_frame_ = false;
 578   send_begin_main_frame_funnel_ = true;
 579   last_frame_number_begin_main_frame_sent_ = current_frame_number_;
 580 }
 581
 582 void SchedulerStateMachine::WillCommit(bool commit_has_no_updates) {
 583   commit_count_++;
 584
 585   // Animate after commit even if we've already animated.
 586   if (!commit_has_no_updates)
 587     animate_funnel_ = false;
 588
 589   if (commit_has_no_updates || settings_.main_frame_before_activation_enabled) {
 590     begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_IDLE;
 591   } else {
 592     begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION;
 593   }
 594
 595   // If the commit was aborted, then there is no pending tree.
 596   has_pending_tree_ = !commit_has_no_updates;
 597
 598   wait_for_ready_to_draw_ =
 599       !commit_has_no_updates && settings_.commit_to_active_tree;
 600
 601   // Update state related to forced draws.
 602   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT) {
 603     forced_redraw_state_ = has_pending_tree_
 604                                ? FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION
 605                                : FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
 606   }
 607
 608   // Update the output surface state.
 609   DCHECK_NE(output_surface_state_, OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION);
 610   if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT) {
 611     if (has_pending_tree_) {
 612       output_surface_state_ = OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION;
 613     } else {
 614       output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
 615     }
 616   }
 617
 618   // Update state if there's no updates heading for the active tree, but we need
 619   // to do a forced draw.
 620   if (commit_has_no_updates &&
 621       forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW) {
 622     DCHECK(!has_pending_tree_);
 623     needs_redraw_ = true;
 624     active_tree_needs_first_draw_ = true;
 625   }
 626
 627   // This post-commit work is common to both completed and aborted commits.
 628   pending_tree_is_ready_for_activation_ = false;
 629
 630   if (continuous_painting_)
 631     needs_begin_main_frame_ = true;
 632   last_commit_had_no_updates_ = commit_has_no_updates;
 633 }
 634
 635 void SchedulerStateMachine::WillActivate() {
 636   if (begin_main_frame_state_ ==
 637       BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION) {
 638     begin_main_frame_state_ = settings_.commit_to_active_tree
 639                                   ? BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW
 640                                   : BEGIN_MAIN_FRAME_STATE_IDLE;
 641   }
 642
 643   if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION)
 644     output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
 645
 646   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION)
 647     forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
 648
 649   has_pending_tree_ = false;
 650   pending_tree_is_ready_for_activation_ = false;
 651   active_tree_needs_first_draw_ = true;
 652   needs_redraw_ = true;
 653 }
 654
 655 void SchedulerStateMachine::WillDraw(bool did_request_swap) {
 656   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
 657     forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
 658
 659   if (begin_main_frame_state_ == BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW)
 660     begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_IDLE;
 661
 662   needs_redraw_ = false;
 663   active_tree_needs_first_draw_ = false;
 664
 665   if (did_request_swap) {
 666     DCHECK(!request_swap_funnel_);
 667     request_swap_funnel_ = true;
 668     did_request_swap_in_last_frame_ = true;
 669     last_frame_number_swap_requested_ = current_frame_number_;
 670   }
 671 }
 672
 673 void SchedulerStateMachine::WillPrepareTiles() {
 674   needs_prepare_tiles_ = false;
 675 }
 676
 677 void SchedulerStateMachine::WillBeginOutputSurfaceCreation() {
 678   DCHECK_EQ(output_surface_state_, OUTPUT_SURFACE_LOST);
 679   output_surface_state_ = OUTPUT_SURFACE_CREATING;
 680
 681   // The following DCHECKs make sure we are in the proper quiescent state.
 682   // The pipeline should be flushed entirely before we start output
 683   // surface creation to avoid complicated corner cases.
 684   DCHECK_EQ(begin_main_frame_state_, BEGIN_MAIN_FRAME_STATE_IDLE);
 685   DCHECK(!has_pending_tree_);
 686   DCHECK(!active_tree_needs_first_draw_);
 687 }
 688
 689 void SchedulerStateMachine::WillInvalidateOutputSurface() {
 690   DCHECK(!invalidate_output_surface_funnel_);
 691   invalidate_output_surface_funnel_ = true;
 692   last_frame_number_invalidate_output_surface_performed_ =
 693       current_frame_number_;
 694
 695   // The synchronous compositor makes no guarantees about a draw coming in after
 696   // an invalidate so clear any flags that would cause the compositor's pipeline
 697   // to stall.
 698   active_tree_needs_first_draw_ = false;  // blocks commit if true
 699 }
 700
 701 void SchedulerStateMachine::SetSkipNextBeginMainFrameToReduceLatency() {
 702   TRACE_EVENT_INSTANT0("cc",
 703                        "Scheduler: SkipNextBeginMainFrameToReduceLatency",
 704                        TRACE_EVENT_SCOPE_THREAD);
 705   skip_next_begin_main_frame_to_reduce_latency_ = true;
 706 }
 707
 708 bool SchedulerStateMachine::BeginFrameRequiredForChildren() const {
 709   return children_need_begin_frames_;
 710 }
 711
 712 bool SchedulerStateMachine::BeginFrameNeededForVideo() const {
 713   return video_needs_begin_frames_;
 714 }
 715
 716 bool SchedulerStateMachine::BeginFrameNeeded() const {
 717   // We can't handle BeginFrames when output surface isn't initialized.
 718   // TODO(brianderson): Support output surface creation inside a BeginFrame.
 719   if (!HasInitializedOutputSurface())
 720     return false;
 721
 722   // If we are not visible, we don't need BeginFrame messages.
 723   if (!visible_)
 724     return false;
 725
 726   return (BeginFrameRequiredForAction() || BeginFrameRequiredForChildren() ||
 727           BeginFrameNeededForVideo() || ProactiveBeginFrameWanted());
 728 }
 729
 730 void SchedulerStateMachine::SetChildrenNeedBeginFrames(
 731     bool children_need_begin_frames) {
 732   children_need_begin_frames_ = children_need_begin_frames;
 733 }
 734
 735 void SchedulerStateMachine::SetVideoNeedsBeginFrames(
 736     bool video_needs_begin_frames) {
 737   video_needs_begin_frames_ = video_needs_begin_frames;
 738 }
 739
 740 void SchedulerStateMachine::SetDeferCommits(bool defer_commits) {
 741   defer_commits_ = defer_commits;
 742 }
 743
 744 // These are the cases where we require a BeginFrame message to make progress
 745 // on requested actions.
 746 bool SchedulerStateMachine::BeginFrameRequiredForAction() const {
 747   // The forced draw respects our normal draw scheduling, so we need to
 748   // request a BeginImplFrame for it.
 749   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
 750     return true;
 751
 752   return needs_animate_ || needs_redraw_ ||
 753          (needs_begin_main_frame_ && !defer_commits_);
 754 }
 755
 756 // These are cases where we are very likely want a BeginFrame message in the
 757 // near future. Proactively requesting the BeginImplFrame helps hide the round
 758 // trip latency of the SetNeedsBeginFrame request that has to go to the
 759 // Browser.
 760 // This includes things like drawing soon, but might not actually have a new
 761 // frame to draw when we receive the next BeginImplFrame.
 762 bool SchedulerStateMachine::ProactiveBeginFrameWanted() const {
 763   // Do not be proactive when invisible.
 764   if (!visible_)
 765     return false;
 766
 767   // We should proactively request a BeginImplFrame if a commit is pending
 768   // because we will want to draw if the commit completes quickly. Do not
 769   // request frames when commits are disabled, because the frame requests will
 770   // not provide the needed commit (and will wake up the process when it could
 771   // stay idle).
 772   if ((begin_main_frame_state_ != BEGIN_MAIN_FRAME_STATE_IDLE) &&
 773       !defer_commits_)
 774     return true;
 775
 776   // If the pending tree activates quickly, we'll want a BeginImplFrame soon
 777   // to draw the new active tree.
 778   if (has_pending_tree_)
 779     return true;
 780
 781   // Changing priorities may allow us to activate (given the new priorities),
 782   // which may result in a new frame.
 783   if (needs_prepare_tiles_)
 784     return true;
 785
 786   // If we just sent a swap request, it's likely that we are going to produce
 787   // another frame soon. This helps avoid negative glitches in our
 788   // SetNeedsBeginFrame requests, which may propagate to the BeginImplFrame
 789   // provider and get sampled at an inopportune time, delaying the next
 790   // BeginImplFrame.
 791   if (did_request_swap_in_last_frame_)
 792     return true;
 793
 794   // If the last commit was aborted because of early out (no updates), we should
 795   // still want a begin frame in case there is a commit coming again.
 796   if (last_commit_had_no_updates_)
 797     return true;
 798
 799   return false;
 800 }
 801
 802 void SchedulerStateMachine::OnBeginImplFrame() {
 803   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING;
 804   current_frame_number_++;
 805
 806   last_commit_had_no_updates_ = false;
 807   did_request_swap_in_last_frame_ = false;
 808
 809   // Clear funnels for any actions we perform during the frame.
 810   animate_funnel_ = false;
 811   send_begin_main_frame_funnel_ = false;
 812   invalidate_output_surface_funnel_ = false;
 813
 814   // "Drain" the PrepareTiles funnel.
 815   if (prepare_tiles_funnel_ > 0)
 816     prepare_tiles_funnel_--;
 817 }
 818
 819 void SchedulerStateMachine::OnBeginImplFrameDeadlinePending() {
 820   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME;
 821 }
 822
 823 void SchedulerStateMachine::OnBeginImplFrameDeadline() {
 824   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE;
 825
 826   did_perform_swap_in_last_draw_ = false;
 827
 828   // Clear funnels for any actions we perform during the deadline.
 829   request_swap_funnel_ = false;
 830
 831   // Allow one PrepareTiles per draw for synchronous compositor.
 832   if (settings_.using_synchronous_renderer_compositor) {
 833     if (prepare_tiles_funnel_ > 0)
 834       prepare_tiles_funnel_--;
 835   }
 836 }
 837
 838 void SchedulerStateMachine::OnBeginImplFrameIdle() {
 839   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_IDLE;
 840
 841   skip_next_begin_main_frame_to_reduce_latency_ = false;
 842
 843   // If a new or undrawn active tree is pending after the deadline,
 844   // then the main thread is in a high latency mode.
 845   main_thread_missed_last_deadline_ =
 846       CommitPending() || has_pending_tree_ || active_tree_needs_first_draw_;
 847
 848   // If we're entering a state where we won't get BeginFrames set all the
 849   // funnels so that we don't perform any actions that we shouldn't.
 850   if (!BeginFrameNeeded())
 851     send_begin_main_frame_funnel_ = true;
 852 }
 853
 854 SchedulerStateMachine::BeginImplFrameDeadlineMode
 855 SchedulerStateMachine::CurrentBeginImplFrameDeadlineMode() const {
 856   if (settings_.using_synchronous_renderer_compositor) {
 857     // No deadline for synchronous compositor.
 858     return BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE;
 859   } else if (ShouldTriggerBeginImplFrameDeadlineImmediately()) {
 860     return BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE;
 861   } else if (wait_for_ready_to_draw_) {
 862     // When we are waiting for ready to draw signal, we do not wait to post a
 863     // deadline yet.
 864     return BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW;
 865   } else if (needs_redraw_ && !SwapThrottled()) {
 866     // We have an animation or fast input path on the impl thread that wants
 867     // to draw, so don't wait too long for a new active tree.
 868     // If we are swap throttled we should wait until we are unblocked.
 869     return BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR;
 870   } else {
 871     // The impl thread doesn't have anything it wants to draw and we are just
 872     // waiting for a new active tree or we are swap throttled. In short we are
 873     // blocked.
 874     return BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE;
 875   }
 876 }
 877
 878 bool SchedulerStateMachine::ShouldTriggerBeginImplFrameDeadlineImmediately()
 879     const {
 880   // If we just forced activation, we should end the deadline right now.
 881   if (PendingActivationsShouldBeForced() && !has_pending_tree_)
 882     return true;
 883
 884   // Do not trigger deadline immediately if we're waiting for READY_TO_DRAW
 885   // unless it's one of the forced cases.
 886   if (wait_for_ready_to_draw_)
 887     return false;
 888
 889   // SwapAck throttle the deadline since we wont draw and swap anyway.
 890   if (SwapThrottled())
 891     return false;
 892
 893   if (active_tree_needs_first_draw_)
 894     return true;
 895
 896   if (!needs_redraw_)
 897     return false;
 898
 899   // This is used to prioritize impl-thread draws when the main thread isn't
 900   // producing anything, e.g., after an aborted commit. We also check that we
 901   // don't have a pending tree -- otherwise we should give it a chance to
 902   // activate.
 903   // TODO(skyostil): Revisit this when we have more accurate deadline estimates.
 904   if (begin_main_frame_state_ == BEGIN_MAIN_FRAME_STATE_IDLE &&
 905       !has_pending_tree_)
 906     return true;
 907
 908   // Prioritize impl-thread draws in impl_latency_takes_priority_ mode.
 909   if (impl_latency_takes_priority_)
 910     return true;
 911
 912   return false;
 913 }
 914
 915 bool SchedulerStateMachine::main_thread_missed_last_deadline() const {
 916   return main_thread_missed_last_deadline_;
 917 }
 918
 919 bool SchedulerStateMachine::SwapThrottled() const {
 920   return pending_swaps_ >= max_pending_swaps_;
 921 }
 922
 923 void SchedulerStateMachine::SetVisible(bool visible) {
 924   if (visible_ == visible)
 925     return;
 926
 927   visible_ = visible;
 928
 929   if (visible)
 930     main_thread_missed_last_deadline_ = false;
 931
 932   // TODO(sunnyps): Change the funnel to a bool to avoid hacks like this.
 933   prepare_tiles_funnel_ = 0;
 934   wait_for_ready_to_draw_ = false;
 935 }
 936
 937 void SchedulerStateMachine::SetCanDraw(bool can_draw) { can_draw_ = can_draw; }
 938
 939 void SchedulerStateMachine::SetNeedsRedraw() { needs_redraw_ = true; }
 940
 941 void SchedulerStateMachine::SetNeedsAnimate() {
 942   needs_animate_ = true;
 943 }
 944
 945 bool SchedulerStateMachine::OnlyImplSideUpdatesExpected() const {
 946   bool has_impl_updates = needs_redraw_ || needs_animate_;
 947   bool main_updates_expected =
 948       needs_begin_main_frame_ ||
 949       begin_main_frame_state_ != BEGIN_MAIN_FRAME_STATE_IDLE ||
 950       has_pending_tree_;
 951   return has_impl_updates && !main_updates_expected;
 952 }
 953
 954 void SchedulerStateMachine::SetNeedsPrepareTiles() {
 955   if (!needs_prepare_tiles_) {
 956     TRACE_EVENT0("cc", "SchedulerStateMachine::SetNeedsPrepareTiles");
 957     needs_prepare_tiles_ = true;
 958   }
 959 }
 960
 961 void SchedulerStateMachine::SetMaxSwapsPending(int max) {
 962   max_pending_swaps_ = max;
 963 }
 964
 965 void SchedulerStateMachine::DidSwapBuffers() {
 966   pending_swaps_++;
 967   swaps_with_current_output_surface_++;
 968
 969   DCHECK_LE(pending_swaps_, max_pending_swaps_);
 970
 971   did_perform_swap_in_last_draw_ = true;
 972   last_frame_number_swap_performed_ = current_frame_number_;
 973 }
 974
 975 void SchedulerStateMachine::DidSwapBuffersComplete() {
 976   pending_swaps_--;
 977 }
 978
 979 void SchedulerStateMachine::SetImplLatencyTakesPriority(
 980     bool impl_latency_takes_priority) {
 981   impl_latency_takes_priority_ = impl_latency_takes_priority;
 982 }
 983
 984 void SchedulerStateMachine::DidDrawIfPossibleCompleted(DrawResult result) {
 985   switch (result) {
 986     case INVALID_RESULT:
 987       NOTREACHED() << "Uninitialized DrawResult.";
 988       break;
 989     case DRAW_ABORTED_CANT_DRAW:
 990     case DRAW_ABORTED_CONTEXT_LOST:
 991       NOTREACHED() << "Invalid return value from DrawAndSwapIfPossible:"
 992                    << result;
 993       break;
 994     case DRAW_SUCCESS:
 995       consecutive_checkerboard_animations_ = 0;
 996       forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
 997       break;
 998     case DRAW_ABORTED_CHECKERBOARD_ANIMATIONS:
 999       needs_redraw_ = true;
1000
1001       // If we're already in the middle of a redraw, we don't need to
1002       // restart it.
1003       if (forced_redraw_state_ != FORCED_REDRAW_STATE_IDLE)
1004         return;
1005
1006       needs_begin_main_frame_ = true;
1007       consecutive_checkerboard_animations_++;
1008       if (settings_.timeout_and_draw_when_animation_checkerboards &&
1009           consecutive_checkerboard_animations_ >=
1010               settings_.maximum_number_of_failed_draws_before_draw_is_forced) {
1011         consecutive_checkerboard_animations_ = 0;
1012         // We need to force a draw, but it doesn't make sense to do this until
1013         // we've committed and have new textures.
1014         forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_COMMIT;
1015       }
1016       break;
1017     case DRAW_ABORTED_MISSING_HIGH_RES_CONTENT:
1018       // It's not clear whether this missing content is because of missing
1019       // pictures (which requires a commit) or because of memory pressure
1020       // removing textures (which might not).  To be safe, request a commit
1021       // anyway.
1022       needs_begin_main_frame_ = true;
1023       break;
1024   }
1025 }
1026
1027 void SchedulerStateMachine::SetNeedsBeginMainFrame() {
1028   needs_begin_main_frame_ = true;
1029 }
1030
1031 void SchedulerStateMachine::NotifyReadyToCommit() {
1032   DCHECK(begin_main_frame_state_ == BEGIN_MAIN_FRAME_STATE_STARTED)
1033       << AsValue()->ToString();
1034   begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT;
1035   // In commit_to_active_tree mode, commit should happen right after
1036   // BeginFrame, meaning when this function is called, next action should be
1037   // commit.
1038   if (settings_.commit_to_active_tree)
1039     DCHECK(ShouldCommit());
1040 }
1041
1042 void SchedulerStateMachine::BeginMainFrameAborted(CommitEarlyOutReason reason) {
1043   DCHECK_EQ(begin_main_frame_state_, BEGIN_MAIN_FRAME_STATE_SENT);
1044   switch (reason) {
1045     case CommitEarlyOutReason::ABORTED_OUTPUT_SURFACE_LOST:
1046     case CommitEarlyOutReason::ABORTED_NOT_VISIBLE:
1047     case CommitEarlyOutReason::ABORTED_DEFERRED_COMMIT:
1048       begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_IDLE;
1049       SetNeedsBeginMainFrame();
1050       return;
1051     case CommitEarlyOutReason::FINISHED_NO_UPDATES:
1052       bool commit_has_no_updates = true;
1053       WillCommit(commit_has_no_updates);
1054       return;
1055   }
1056 }
1057
1058 void SchedulerStateMachine::DidPrepareTiles() {
1059   needs_prepare_tiles_ = false;
1060   // "Fill" the PrepareTiles funnel.
1061   prepare_tiles_funnel_++;
1062 }
1063
1064 void SchedulerStateMachine::DidLoseOutputSurface() {
1065   if (output_surface_state_ == OUTPUT_SURFACE_LOST ||
1066       output_surface_state_ == OUTPUT_SURFACE_CREATING)
1067     return;
1068   output_surface_state_ = OUTPUT_SURFACE_LOST;
1069   needs_redraw_ = false;
1070   wait_for_ready_to_draw_ = false;
1071 }
1072
1073 void SchedulerStateMachine::NotifyReadyToActivate() {
1074   if (has_pending_tree_)
1075     pending_tree_is_ready_for_activation_ = true;
1076 }
1077
1078 void SchedulerStateMachine::NotifyReadyToDraw() {
1079   wait_for_ready_to_draw_ = false;
1080 }
1081
1082 void SchedulerStateMachine::DidCreateAndInitializeOutputSurface() {
1083   DCHECK_EQ(output_surface_state_, OUTPUT_SURFACE_CREATING);
1084   output_surface_state_ = OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT;
1085
1086   if (did_create_and_initialize_first_output_surface_) {
1087     // TODO(boliu): See if we can remove this when impl-side painting is always
1088     // on. Does anything on the main thread need to update after recreate?
1089     needs_begin_main_frame_ = true;
1090   }
1091   did_create_and_initialize_first_output_surface_ = true;
1092   pending_swaps_ = 0;
1093   swaps_with_current_output_surface_ = 0;
1094   main_thread_missed_last_deadline_ = false;
1095 }
1096
1097 void SchedulerStateMachine::NotifyBeginMainFrameStarted() {
1098   DCHECK_EQ(begin_main_frame_state_, BEGIN_MAIN_FRAME_STATE_SENT);
1099   begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_STARTED;
1100 }
1101
1102 bool SchedulerStateMachine::HasInitializedOutputSurface() const {
1103   switch (output_surface_state_) {
1104     case OUTPUT_SURFACE_LOST:
1105     case OUTPUT_SURFACE_CREATING:
1106       return false;
1107
1108     case OUTPUT_SURFACE_ACTIVE:
1109     case OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT:
1110     case OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION:
1111       return true;
1112   }
1113   NOTREACHED();
1114   return false;
1115 }
1116
1117 }  // namespace cc