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