cc: Use multiple PrepareTiles approaches

cc/scheduler/scheduler_state_machine.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/scheduler/scheduler_state_machine.h"
 
 #include "base/format_macros.h"
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
 #include "base/values.h"
 #include "ui/gfx/frame_time.h"
 
 namespace cc {
 
 SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
     : settings_(settings),
       output_surface_state_(OUTPUT_SURFACE_LOST),
       begin_impl_frame_state_(BEGIN_IMPL_FRAME_STATE_IDLE),
       commit_state_(COMMIT_STATE_IDLE),
-      forced_redraw_state_(FORCED_REDRAW_STATE_IDLE),
+      prepare_tiles_approach_(PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY),
+      prepare_tiles_reason_(PREPARE_TILES_NOT_NEEDED),
       commit_count_(0),
       current_frame_number_(0),
       last_frame_number_animate_performed_(-1),
       last_frame_number_swap_performed_(-1),
       last_frame_number_swap_requested_(-1),
       last_frame_number_begin_main_frame_sent_(-1),
       last_frame_number_invalidate_output_surface_performed_(-1),
       animate_funnel_(false),
       request_swap_funnel_(false),
       send_begin_main_frame_funnel_(false),
       invalidate_output_surface_funnel_(false),
       prepare_tiles_funnel_(0),
-      consecutive_checkerboard_animations_(0),
       max_pending_swaps_(1),
       pending_swaps_(0),
       needs_redraw_(false),
+      last_draw_result_(DRAW_SUCCESS),
       needs_animate_(false),
-      needs_prepare_tiles_(false),
       needs_commit_(false),
       visible_(false),
       can_start_(false),
       can_draw_(false),
       has_pending_tree_(false),
       pending_tree_is_ready_for_activation_(false),
+      requires_high_res_to_draw_(false),
       active_tree_needs_first_draw_(false),
       did_create_and_initialize_first_output_surface_(false),
       impl_latency_takes_priority_(false),
       skip_next_begin_main_frame_to_reduce_latency_(false),
       skip_begin_main_frame_to_reduce_latency_(false),
       continuous_painting_(false),
       children_need_begin_frames_(false),
       defer_commits_(false),
       video_needs_begin_frames_(false),
       last_commit_had_no_updates_(false),
@@ skipping 40 matching lines @@
     BeginImplFrameDeadlineMode mode) {
   switch (mode) {
     case BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE:
       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE";
     case BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE:
       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE";
     case BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR:
       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR";
     case BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE:
       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE";
+    case BEGIN_IMPL_FRAME_DEADLINE_MODE_TRY_TO_AVOID_CHECKERBOARD:
+      return "BEGIN_IMPL_FRAME_DEADLINE_MODE_TRY_TO_AVOID_CHECKERBOARD";
     case BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW:
       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW";
   }
   NOTREACHED();
   return "???";
 }
 
 const char* SchedulerStateMachine::CommitStateToString(CommitState state) {
   switch (state) {
     case COMMIT_STATE_IDLE:
       return "COMMIT_STATE_IDLE";
     case COMMIT_STATE_BEGIN_MAIN_FRAME_SENT:
       return "COMMIT_STATE_BEGIN_MAIN_FRAME_SENT";
     case COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED:
       return "COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED";
     case COMMIT_STATE_READY_TO_COMMIT:
       return "COMMIT_STATE_READY_TO_COMMIT";
     case COMMIT_STATE_WAITING_FOR_ACTIVATION:
       return "COMMIT_STATE_WAITING_FOR_ACTIVATION";
     case COMMIT_STATE_WAITING_FOR_DRAW:
       return "COMMIT_STATE_WAITING_FOR_DRAW";
   }
   NOTREACHED();
   return "???";
 }
 
-const char* SchedulerStateMachine::ForcedRedrawOnTimeoutStateToString(
-    ForcedRedrawOnTimeoutState state) {
-  switch (state) {
-    case FORCED_REDRAW_STATE_IDLE:
-      return "FORCED_REDRAW_STATE_IDLE";
-    case FORCED_REDRAW_STATE_WAITING_FOR_COMMIT:
-      return "FORCED_REDRAW_STATE_WAITING_FOR_COMMIT";
-    case FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION:
-      return "FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION";
-    case FORCED_REDRAW_STATE_WAITING_FOR_DRAW:
-      return "FORCED_REDRAW_STATE_WAITING_FOR_DRAW";
+const char* SchedulerStateMachine::PrepareTilesApproachToString(
+    PrepareTilesApproach approach) {
+  switch (approach) {
+    case PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY:
+      return "PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY";
+    case PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_WORK:
+      return "PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_WORK";
+    case PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_PENDING_WORK:
+      return "PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_PENDING_WORK";
+    case PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_PENDING_CANCELED_WORK:
+      return "PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_PENDING_CANCELED_WORK";
   }
   NOTREACHED();
   return "???";
+}
+
+const char* SchedulerStateMachine::PrepareTilesReasonToString(
+    PrepareTilesReason reason) {
+  switch (reason) {
+    case PREPARE_TILES_NOT_NEEDED:
+      return "PREPARE_TILES_NOT_NEEDED";
+    case PREPARE_TILES_REQUESTED:
+      return "PREPARE_TILES_REQUESTED";
+    case PREPARE_TILES_NEEDED_FOR_COMMIT:
+      return "PREPARE_TILES_NEEDED_FOR_COMMIT";
+    case PREPARE_TILES_NEEDED_FOR_ACTIVATION:
+      return "PREPARE_TILES_NEEDED_FOR_ACTIVATION";
+    case PREPARE_TILES_NEEDED_FOR_ABORTED_DRAW:
+      return "PREPARE_TILES_NEEDED_FOR_ABORTED_DRAW";
+    case PREPARE_TILES_NEEDED_TO_EVICT_TILES:
+      return "PREPARE_TILES_NEEDED_TO_EVICT_TILES";
+  }
+  NOTREACHED();
+  return "???";
 }
 
 const char* SchedulerStateMachine::ActionToString(Action action) {
   switch (action) {
     case ACTION_NONE:
       return "ACTION_NONE";
     case ACTION_ANIMATE:
       return "ACTION_ANIMATE";
     case ACTION_SEND_BEGIN_MAIN_FRAME:
       return "ACTION_SEND_BEGIN_MAIN_FRAME";
@@ skipping 26 matching lines @@
   return state;
 }
 
 void SchedulerStateMachine::AsValueInto(
     base::trace_event::TracedValue* state) const {
   state->BeginDictionary("major_state");
   state->SetString("next_action", ActionToString(NextAction()));
   state->SetString("begin_impl_frame_state",
                    BeginImplFrameStateToString(begin_impl_frame_state_));
   state->SetString("commit_state", CommitStateToString(commit_state_));
-  state->SetString("output_surface_state_",
+  state->SetString("prepare_tiles_approach",
+                   PrepareTilesApproachToString(prepare_tiles_approach_));
+  state->SetString("prepare_tiles_reason",
+                   PrepareTilesReasonToString(prepare_tiles_reason_));
+  state->SetString("output_surface_state",
                    OutputSurfaceStateToString(output_surface_state_));
-  state->SetString("forced_redraw_state",
-                   ForcedRedrawOnTimeoutStateToString(forced_redraw_state_));
   state->EndDictionary();
 
   state->BeginDictionary("minor_state");
   state->SetInteger("commit_count", commit_count_);
   state->SetInteger("current_frame_number", current_frame_number_);
   state->SetInteger("last_frame_number_animate_performed",
                     last_frame_number_animate_performed_);
   state->SetInteger("last_frame_number_swap_performed",
                     last_frame_number_swap_performed_);
   state->SetInteger("last_frame_number_swap_requested",
                     last_frame_number_swap_requested_);
   state->SetInteger("last_frame_number_begin_main_frame_sent",
                     last_frame_number_begin_main_frame_sent_);
   state->SetBoolean("funnel: animate_funnel", animate_funnel_);
   state->SetBoolean("funnel: request_swap_funnel", request_swap_funnel_);
   state->SetBoolean("funnel: send_begin_main_frame_funnel",
                     send_begin_main_frame_funnel_);
   state->SetInteger("funnel: prepare_tiles_funnel", prepare_tiles_funnel_);
   state->SetBoolean("funnel: invalidate_output_surface_funnel",
                     invalidate_output_surface_funnel_);
-  state->SetInteger("consecutive_checkerboard_animations",
-                    consecutive_checkerboard_animations_);
   state->SetInteger("max_pending_swaps_", max_pending_swaps_);
   state->SetInteger("pending_swaps_", pending_swaps_);
   state->SetBoolean("needs_redraw", needs_redraw_);
   state->SetBoolean("needs_animate_", needs_animate_);
-  state->SetBoolean("needs_prepare_tiles", needs_prepare_tiles_);
   state->SetBoolean("needs_commit", needs_commit_);
   state->SetBoolean("visible", visible_);
   state->SetBoolean("can_start", can_start_);
   state->SetBoolean("can_draw", can_draw_);
   state->SetBoolean("has_pending_tree", has_pending_tree_);
   state->SetBoolean("pending_tree_is_ready_for_activation",
                     pending_tree_is_ready_for_activation_);
   state->SetBoolean("active_tree_needs_first_draw",
                     active_tree_needs_first_draw_);
   state->SetBoolean("wait_for_active_tree_ready_to_draw",
@@ skipping 104 matching lines @@
 
   // Do not queue too many swaps.
   if (pending_swaps_ >= max_pending_swaps_)
     return false;
 
   // Except for the cases above, do not draw outside of the BeginImplFrame
   // deadline.
   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
     return false;
 
-  // Only handle forced redraws due to timeouts on the regular deadline.
-  if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
-    return true;
-
   return needs_redraw_;
 }
 
 bool SchedulerStateMachine::ShouldActivatePendingTree() const {
   // There is nothing to activate.
   if (!has_pending_tree_)
     return false;
 
   // We should not activate a second tree before drawing the first one.
   // Even if we need to force activation of the pending tree, we should abort
@@ skipping 61 matching lines @@
 
   // We should not send BeginMainFrame while we are in
   // BEGIN_IMPL_FRAME_STATE_IDLE since we might have new
   // user input arriving soon.
   // TODO(brianderson): Allow sending BeginMainFrame while idle when the main
   // thread isn't consuming user input.
   if (begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_IDLE &&
       BeginFrameNeeded())
     return false;
 
-  // We need a new commit for the forced redraw. This honors the
-  // single commit per interval because the result will be swapped to screen.
-  if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT)
-    return true;
-
   // We shouldn't normally accept commits if there isn't an OutputSurface.
   if (!HasInitializedOutputSurface())
     return false;
 
   // SwapAck throttle the BeginMainFrames unless we just swapped.
   // TODO(brianderson): Remove this restriction to improve throughput.
   bool just_swapped_in_deadline =
       begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE &&
       did_perform_swap_in_last_draw_;
   if (pending_swaps_ >= max_pending_swaps_ && !just_swapped_in_deadline)
@@ skipping 16 matching lines @@
   }
 
   // Prioritize drawing the previous commit before finishing the next commit.
   if (active_tree_needs_first_draw_)
     return false;
 
   return true;
 }
 
 bool SchedulerStateMachine::ShouldPrepareTiles() const {
-  // PrepareTiles only really needs to be called immediately after commit
-  // and then periodically after that. Use a funnel to make sure we average
-  // one PrepareTiles per BeginImplFrame in the long run.
-  if (prepare_tiles_funnel_ > 0)
-    return false;
+  // Handle the clear cut cases.
+  switch (prepare_tiles_reason_) {
+    case PREPARE_TILES_NOT_NEEDED:
+      return false;
+    case PREPARE_TILES_NEEDED_FOR_COMMIT:
+    case PREPARE_TILES_NEEDED_FOR_ACTIVATION:
+    case PREPARE_TILES_NEEDED_FOR_ABORTED_DRAW:
+    case PREPARE_TILES_NEEDED_TO_EVICT_TILES:
+      return true;
+    case PREPARE_TILES_REQUESTED:
+      break;
+  }
 
-  // Limiting to once per-frame is not enough, since we only want to
-  // prepare tiles _after_ draws.
-  if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
-    return false;
+  switch (prepare_tiles_approach_) {
+    case PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_WORK:
+    case PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_PENDING_WORK:
+    case PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_PENDING_CANCELED_WORK:
+      // All of these approaches only handle requested PrepareTiles at the
+      // start of a frame.
+      return begin_impl_frame_state_ ==
+             BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING;
+    case PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY:
+      break;
+  }
 
-  return needs_prepare_tiles_;
+  DCHECK_EQ(PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY, prepare_tiles_approach_);
+  DCHECK_EQ(PREPARE_TILES_REQUESTED, prepare_tiles_reason_);
+
+  // Only PrepareTiles after a draw if we haven't already PreparedTiles this
+  // frame. This takes PrepareTiles out of the critical path, but wil make the
+  // NotifyReadyToDraw and NotifyReadyToActivate signals liars.
+  bool did_not_prepare_tiles_at_end_of_frame =
+      prepare_tiles_funnel_ == 0 &&
+      begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE;
+  return did_not_prepare_tiles_at_end_of_frame;
 }
 
 bool SchedulerStateMachine::ShouldInvalidateOutputSurface() const {
   // Do not invalidate too many times in a frame.
   if (invalidate_output_surface_funnel_)
     return false;
 
   // Only the synchronous compositor requires invalidations.
   if (!settings_.using_synchronous_renderer_compositor)
     return false;
 
   // Invalidations are only performed inside a BeginFrame.
   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING)
     return false;
 
+  // TODO(brianderson): Figure out what to do with this.
   // TODO(sunnyps): needs_prepare_tiles_ is needed here because PrepareTiles is
   // called only inside the deadline / draw phase. We could remove this if we
   // allowed PrepareTiles to happen in OnBeginImplFrame.
-  return needs_redraw_ || needs_prepare_tiles_;
+  return needs_redraw_ || PrepareTilesPending();
 }
 
 SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
   if (ShouldActivatePendingTree())
     return ACTION_ACTIVATE_SYNC_TREE;
   if (ShouldCommit())
     return ACTION_COMMIT;
   if (ShouldAnimate())
     return ACTION_ANIMATE;
   if (ShouldDraw()) {
     if (PendingDrawsShouldBeAborted())
       return ACTION_DRAW_AND_SWAP_ABORT;
-    else if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
+    else if (requires_high_res_to_draw_ ||
+             prepare_tiles_approach_ ==
+                 PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY)
+      return ACTION_DRAW_AND_SWAP_IF_POSSIBLE;
+    else
       return ACTION_DRAW_AND_SWAP_FORCED;
-    else
-      return ACTION_DRAW_AND_SWAP_IF_POSSIBLE;
   }
   if (ShouldPrepareTiles())
     return ACTION_PREPARE_TILES;
   if (ShouldSendBeginMainFrame())
     return ACTION_SEND_BEGIN_MAIN_FRAME;
   if (ShouldInvalidateOutputSurface())
     return ACTION_INVALIDATE_OUTPUT_SURFACE;
   if (ShouldBeginOutputSurfaceCreation())
     return ACTION_BEGIN_OUTPUT_SURFACE_CREATION;
   return ACTION_NONE;
@@ skipping 82 matching lines @@
   } else {
     commit_state_ = settings_.main_thread_should_always_be_low_latency
                         ? COMMIT_STATE_WAITING_FOR_DRAW
                         : COMMIT_STATE_IDLE;
   }
 
   // If we are impl-side-painting but the commit was aborted, then we behave
   // mostly as if we are not impl-side-painting since there is no pending tree.
   has_pending_tree_ = settings_.impl_side_painting && !commit_has_no_updates;
 
-  // Update state related to forced draws.
-  if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT) {
-    forced_redraw_state_ = has_pending_tree_
-                               ? FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION
-                               : FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
-  }
-
   // Update the output surface state.
   DCHECK_NE(output_surface_state_, OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION);
   if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT) {
     if (has_pending_tree_) {
       output_surface_state_ = OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION;
     } else {
       output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
       needs_redraw_ = true;
     }
   }
 
-  // Update state if we have a new active tree to draw, or if the active tree
-  // was unchanged but we need to do a forced draw.
-  if (!has_pending_tree_ &&
-      (!commit_has_no_updates ||
-       forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)) {
+  // Update state if we have a new active tree to draw.
+  if (!has_pending_tree_) {
     needs_redraw_ = true;
     active_tree_needs_first_draw_ = true;
   }
 
   // This post-commit work is common to both completed and aborted commits.
   pending_tree_is_ready_for_activation_ = false;
 
   if (continuous_painting_)
     needs_commit_ = true;
   last_commit_had_no_updates_ = commit_has_no_updates;
 }
 
 void SchedulerStateMachine::UpdateStateOnActivation() {
   if (commit_state_ == COMMIT_STATE_WAITING_FOR_ACTIVATION) {
     commit_state_ = settings_.main_thread_should_always_be_low_latency
                         ? COMMIT_STATE_WAITING_FOR_DRAW
                         : COMMIT_STATE_IDLE;
   }
 
   if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION)
     output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
 
-  if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION)
-    forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
+  // Make sure to cancel any old active tree work if needed.
+  if (prepare_tiles_approach_ ==
+      PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_PENDING_CANCELED_WORK)
+    prepare_tiles_reason_ = PREPARE_TILES_NEEDED_FOR_ACTIVATION;
 
   has_pending_tree_ = false;
   pending_tree_is_ready_for_activation_ = false;
   active_tree_needs_first_draw_ = true;
   needs_redraw_ = true;
 }
 
 void SchedulerStateMachine::UpdateStateOnDraw(bool did_request_swap) {
-  if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
-    forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
-
   if (commit_state_ == COMMIT_STATE_WAITING_FOR_DRAW)
     commit_state_ = COMMIT_STATE_IDLE;
 
   needs_redraw_ = false;
   active_tree_needs_first_draw_ = false;
 
   if (did_request_swap) {
     DCHECK(!request_swap_funnel_);
     request_swap_funnel_ = true;
     did_request_swap_in_last_frame_ = true;
     last_frame_number_swap_requested_ = current_frame_number_;
   }
+
+  switch (last_draw_result_) {
+    case INVALID_RESULT:
+      NOTREACHED() << "Uninitialized DrawResult.";
+      break;
+
+    case DRAW_ABORTED_CANT_DRAW:
+    case DRAW_ABORTED_CONTEXT_LOST:
+      NOTREACHED() << "Invalid return value from DrawAndSwapIfPossible:"
+                   << last_draw_result_;
+      break;
+
+    case DRAW_SUCCESS:
+      break;
+
+    case DRAW_ABORTED_MISSING_RASTER_OUTPUT_HIGH_RES:
+    case DRAW_ABORTED_MISSING_RASTER_OUTPUT_ANY:
+      TRACE_EVENT_INSTANT0("cc", "Raster missing output.",
+                           TRACE_EVENT_SCOPE_THREAD);
+      prepare_tiles_reason_ = PREPARE_TILES_NEEDED_FOR_ABORTED_DRAW;
+      if (prepare_tiles_approach_ ==
+          PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY) {
+        prepare_tiles_approach_ = PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_WORK;
+      }
+      needs_redraw_ = true;
+      // TODO(brianderson): reschedule the deadline.
+      break;
+
+    case DRAW_ABORTED_MISSING_RASTER_SOURCE:
+      TRACE_EVENT_INSTANT0("cc", "Raster missing source.",
+                           TRACE_EVENT_SCOPE_THREAD);
+      prepare_tiles_reason_ = PREPARE_TILES_NEEDED_FOR_ABORTED_DRAW;
+      if (prepare_tiles_approach_ ==
+          PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY) {
+        prepare_tiles_approach_ = PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_WORK;
+      }
+      // This is one of the few cases where we actively avoid drawing a commit.
+      // Skipping draw of the commit can be better than a flash of checkerboard.
+      active_tree_needs_first_draw_ = false;
+      // We need a new commit to get an updated raster source.
+      needs_commit_ = true;
+      // TODO(brianderson): reschedule the deadline.
+      break;
+  }
 }
 
 void SchedulerStateMachine::UpdateStateOnPrepareTiles() {
-  needs_prepare_tiles_ = false;
+  prepare_tiles_reason_ = PREPARE_TILES_NOT_NEEDED;
+
+  active_tree_ready_to_draw_ = false;
+
+  if (prepare_tiles_approach_ == PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY)
+    prepare_tiles_funnel_++;
+  else
+    prepare_tiles_funnel_ = 0;
 }
 
 void SchedulerStateMachine::UpdateStateOnBeginOutputSurfaceCreation() {
   DCHECK_EQ(output_surface_state_, OUTPUT_SURFACE_LOST);
   output_surface_state_ = OUTPUT_SURFACE_CREATING;
 
   // The following DCHECKs make sure we are in the proper quiescent state.
   // The pipeline should be flushed entirely before we start output
   // surface creation to avoid complicated corner cases.
   DCHECK_EQ(commit_state_, COMMIT_STATE_IDLE);
@@ skipping 44 matching lines @@
 void SchedulerStateMachine::SetChildrenNeedBeginFrames(
     bool children_need_begin_frames) {
   children_need_begin_frames_ = children_need_begin_frames;
 }
 
 void SchedulerStateMachine::SetVideoNeedsBeginFrames(
     bool video_needs_begin_frames) {
   video_needs_begin_frames_ = video_needs_begin_frames;
 }
 
+void SchedulerStateMachine::NotifyBeginFrameSourceActive(bool active) {
+  // Upon becoming inactive, switch back to prioritizing latency.
+  if (!active &&
+      prepare_tiles_approach_ == PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_WORK)
+    prepare_tiles_approach_ = PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY;
+}
+
 void SchedulerStateMachine::SetDeferCommits(bool defer_commits) {
   defer_commits_ = defer_commits;
 }
 
 // These are the cases where we require a BeginFrame message to make progress
 // on requested actions.
 bool SchedulerStateMachine::BeginFrameRequiredForAction() const {
-  // The forced draw respects our normal draw scheduling, so we need to
-  // request a BeginImplFrame for it.
-  if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
-    return true;
-
   return needs_animate_ || needs_redraw_ || (needs_commit_ && !defer_commits_);
 }
 
 // These are cases where we are very likely want a BeginFrame message in the
 // near future. Proactively requesting the BeginImplFrame helps hide the round
 // trip latency of the SetNeedsBeginFrame request that has to go to the
 // Browser.
 // This includes things like drawing soon, but might not actually have a new
 // frame to draw when we receive the next BeginImplFrame.
 bool SchedulerStateMachine::ProactiveBeginFrameWanted() const {
   // Do not be proactive when invisible.
   if (!visible_)
     return false;
 
   // We should proactively request a BeginImplFrame if a commit is pending
   // because we will want to draw if the commit completes quickly. Do not
   // request frames when commits are disabled, because the frame requests will
   // not provide the needed commit (and will wake up the process when it could
   // stay idle).
   if ((commit_state_ != COMMIT_STATE_IDLE) && !defer_commits_)
     return true;
 
   // If the pending tree activates quickly, we'll want a BeginImplFrame soon
   // to draw the new active tree.
   if (has_pending_tree_)
     return true;
 
   // Changing priorities may allow us to activate (given the new priorities),
   // which may result in a new frame.
-  if (needs_prepare_tiles_)
+  if (PrepareTilesPending())
     return true;
 
   // If we just sent a swap request, it's likely that we are going to produce
   // another frame soon. This helps avoid negative glitches in our
   // SetNeedsBeginFrame requests, which may propagate to the BeginImplFrame
   // provider and get sampled at an inopportune time, delaying the next
   // BeginImplFrame.
   if (did_request_swap_in_last_frame_)
     return true;
 
@@ skipping 14 matching lines @@
 
   // Clear funnels for any actions we perform during the frame.
   animate_funnel_ = false;
   send_begin_main_frame_funnel_ = false;
   invalidate_output_surface_funnel_ = false;
 
   // "Drain" the PrepareTiles funnel.
   if (prepare_tiles_funnel_ > 0)
     prepare_tiles_funnel_--;
 
+  // PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_WORK doesn't work well in
+  // main thread low-latency mode. Transition back to
+  // PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY if we just recovered
+  // main-thread latency.
+  if (skip_begin_main_frame_to_reduce_latency_ &&
+      prepare_tiles_approach_ == PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_WORK) {
+    prepare_tiles_approach_ = PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY;
+  }
+
   skip_begin_main_frame_to_reduce_latency_ =
       skip_next_begin_main_frame_to_reduce_latency_;
   skip_next_begin_main_frame_to_reduce_latency_ = false;
 }
 
 void SchedulerStateMachine::OnBeginImplFrameDeadlinePending() {
   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME;
 }
 
 void SchedulerStateMachine::OnBeginImplFrameDeadline() {
@@ skipping 13 matching lines @@
 SchedulerStateMachine::CurrentBeginImplFrameDeadlineMode() const {
   if (settings_.using_synchronous_renderer_compositor) {
     // No deadline for synchronous compositor.
     return BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE;
   } else if (wait_for_active_tree_ready_to_draw_) {
     // When we are waiting for ready to draw signal, we do not wait to post a
     // deadline yet.
     return BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW;
   } else if (ShouldTriggerBeginImplFrameDeadlineImmediately()) {
     return BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE;
-  } else if (needs_redraw_ && pending_swaps_ < max_pending_swaps_) {
-    // We have an animation or fast input path on the impl thread that wants
-    // to draw, so don't wait too long for a new active tree.
-    // If we are swap throttled we should wait until we are unblocked.
-    return BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR;
-  } else {
-    // The impl thread doesn't have anything it wants to draw and we are just
-    // waiting for a new active tree or we are swap throttled. In short we are
-    // blocked.
-    return BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE;
   }
+
+  if (prepare_tiles_approach_ == PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY) {
+    if (needs_redraw_ && pending_swaps_ < max_pending_swaps_) {
+      // We have an animation or fast input path on the impl thread that wants
+      // to draw, so don't wait too long for a new active tree.
+      // If we are swap throttled we should wait until we are unblocked.
+      return BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR;
+    } else {
+      // The impl thread doesn't have anything it wants to draw and we are just
+      // waiting for a new active tree or we are swap throttled. In short we are
+      // blocked.
+      return BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE;
+    }
+  }
+
+  return BEGIN_IMPL_FRAME_DEADLINE_MODE_TRY_TO_AVOID_CHECKERBOARD;
 }
 
 bool SchedulerStateMachine::ShouldTriggerBeginImplFrameDeadlineImmediately()
     const {
   // TODO(brianderson): This should take into account multiple commit sources.
   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME)
     return false;
 
   // If we just forced activation, we should end the deadline right now.
   if (PendingActivationsShouldBeForced() && !has_pending_tree_)
     return true;
 
   // SwapAck throttle the deadline since we wont draw and swap anyway.
   if (pending_swaps_ >= max_pending_swaps_)
     return false;
 
+  // PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY is the only approach
+  // where we want to trigger the deadline before NotifyReadyToDraw.
+  if (prepare_tiles_approach_ != PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY)
+    return active_tree_ready_to_draw_;
+
   if (active_tree_needs_first_draw_)
     return true;
 
   if (!needs_redraw_)
     return false;
 
   // This is used to prioritize impl-thread draws when the main thread isn't
   // producing anything, e.g., after an aborted commit. We also check that we
   // don't have a pending tree -- otherwise we should give it a chance to
   // activate.
@@ skipping 42 matching lines @@
     // which case the main thread is in a high latency mode.
     return (active_tree_needs_first_draw_ || did_perform_swap_in_last_draw_) &&
            !send_begin_main_frame_funnel_;
   }
 
   // If the active tree needs its first draw in any other state, we know the
   // main thread is in a high latency mode.
   return active_tree_needs_first_draw_;
 }
 
-void SchedulerStateMachine::SetVisible(bool visible) { visible_ = visible; }
+void SchedulerStateMachine::SetVisible(bool visible) {
+  visible_ = visible;
+  if (!visible)
+    prepare_tiles_reason_ = PREPARE_TILES_NEEDED_TO_EVICT_TILES;
+}
 
 void SchedulerStateMachine::SetCanDraw(bool can_draw) { can_draw_ = can_draw; }
 
 void SchedulerStateMachine::SetNeedsRedraw() { needs_redraw_ = true; }
 
 void SchedulerStateMachine::SetNeedsAnimate() {
   needs_animate_ = true;
 }
 
 void SchedulerStateMachine::SetWaitForReadyToDraw() {
   DCHECK(settings_.impl_side_painting);
   wait_for_active_tree_ready_to_draw_ = true;
 }
 
-void SchedulerStateMachine::SetNeedsPrepareTiles() {
-  if (!needs_prepare_tiles_) {
-    TRACE_EVENT0("cc", "SchedulerStateMachine::SetNeedsPrepareTiles");
-    needs_prepare_tiles_ = true;
+void SchedulerStateMachine::SetNeedsPrepareTiles(bool for_commit) {
+  TRACE_EVENT0("cc", "SchedulerStateMachine::SetNeedsPrepareTiles");
+  switch (prepare_tiles_approach_) {
+    case PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY:
+    case PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_PENDING_WORK:
+    case PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_PENDING_CANCELED_WORK:
+      if (for_commit)
+        prepare_tiles_reason_ = PREPARE_TILES_NEEDED_FOR_COMMIT;
+      else if (prepare_tiles_reason_ == PREPARE_TILES_NOT_NEEDED)
+        prepare_tiles_reason_ = PREPARE_TILES_REQUESTED;
+      break;
+
+    case PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_WORK:
+      // We don't uncondititionally PrepareTiles immediately after a commit with
+      // this approach.
+      if (prepare_tiles_reason_ == PREPARE_TILES_NOT_NEEDED)
+        prepare_tiles_reason_ = PREPARE_TILES_REQUESTED;
+      break;
   }
 }
 
 void SchedulerStateMachine::SetMaxSwapsPending(int max) {
   max_pending_swaps_ = max;
 }
 
 void SchedulerStateMachine::DidSwapBuffers() {
   pending_swaps_++;
   DCHECK_LE(pending_swaps_, max_pending_swaps_);
 
   did_perform_swap_in_last_draw_ = true;
   last_frame_number_swap_performed_ = current_frame_number_;
 }
 
 void SchedulerStateMachine::DidSwapBuffersComplete() {
   DCHECK_GT(pending_swaps_, 0);
   pending_swaps_--;
 }
 
 void SchedulerStateMachine::SetImplLatencyTakesPriority(
     bool impl_latency_takes_priority) {
   impl_latency_takes_priority_ = impl_latency_takes_priority;
 }
 
-void SchedulerStateMachine::DidDrawIfPossibleCompleted(DrawResult result) {
-  switch (result) {
-    case INVALID_RESULT:
-      NOTREACHED() << "Uninitialized DrawResult.";
-      break;
-    case DRAW_ABORTED_CANT_DRAW:
-    case DRAW_ABORTED_CONTEXT_LOST:
-      NOTREACHED() << "Invalid return value from DrawAndSwapIfPossible:"
-                   << result;
-      break;
-    case DRAW_SUCCESS:
-      consecutive_checkerboard_animations_ = 0;
-      forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
-      break;
-    case DRAW_ABORTED_CHECKERBOARD_ANIMATIONS:
-      needs_redraw_ = true;
-
-      // If we're already in the middle of a redraw, we don't need to
-      // restart it.
-      if (forced_redraw_state_ != FORCED_REDRAW_STATE_IDLE)
-        return;
-
-      needs_commit_ = true;
-      consecutive_checkerboard_animations_++;
-      if (settings_.timeout_and_draw_when_animation_checkerboards &&
-          consecutive_checkerboard_animations_ >=
-              settings_.maximum_number_of_failed_draws_before_draw_is_forced_) {
-        consecutive_checkerboard_animations_ = 0;
-        // We need to force a draw, but it doesn't make sense to do this until
-        // we've committed and have new textures.
-        forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_COMMIT;
-      }
-      break;
-    case DRAW_ABORTED_MISSING_HIGH_RES_CONTENT:
-      // It's not clear whether this missing content is because of missing
-      // pictures (which requires a commit) or because of memory pressure
-      // removing textures (which might not).  To be safe, request a commit
-      // anyway.
-      needs_commit_ = true;
-      break;
-  }
+void SchedulerStateMachine::SetDrawResult(DrawResult result) {
+  last_draw_result_ = result;
 }
 
 void SchedulerStateMachine::SetNeedsCommit() {
   needs_commit_ = true;
 }
 
 void SchedulerStateMachine::NotifyReadyToCommit() {
   DCHECK(commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED)
       << AsValue()->ToString();
   commit_state_ = COMMIT_STATE_READY_TO_COMMIT;
@@ skipping 13 matching lines @@
       commit_state_ = COMMIT_STATE_IDLE;
       SetNeedsCommit();
       return;
     case CommitEarlyOutReason::FINISHED_NO_UPDATES:
       bool commit_has_no_updates = true;
       UpdateStateOnCommit(commit_has_no_updates);
       return;
   }
 }
 
-void SchedulerStateMachine::DidPrepareTiles() {
-  needs_prepare_tiles_ = false;
-  // "Fill" the PrepareTiles funnel.
-  prepare_tiles_funnel_++;
-}
-
 void SchedulerStateMachine::DidLoseOutputSurface() {
   if (output_surface_state_ == OUTPUT_SURFACE_LOST ||
       output_surface_state_ == OUTPUT_SURFACE_CREATING)
     return;
   output_surface_state_ = OUTPUT_SURFACE_LOST;
   needs_redraw_ = false;
   wait_for_active_tree_ready_to_draw_ = false;
 }
 
 void SchedulerStateMachine::NotifyReadyToActivate() {
   if (has_pending_tree_)
     pending_tree_is_ready_for_activation_ = true;
 }
 
 void SchedulerStateMachine::NotifyReadyToDraw() {
   wait_for_active_tree_ready_to_draw_ = false;
+  active_tree_ready_to_draw_ = true;
+}
+
+void SchedulerStateMachine::SetRequiresHighResToDraw(bool required) {
+  if (requires_high_res_to_draw_ == required)
+    return;
+  requires_high_res_to_draw_ = required;
 }
 
 void SchedulerStateMachine::DidCreateAndInitializeOutputSurface() {
   DCHECK_EQ(output_surface_state_, OUTPUT_SURFACE_CREATING);
   output_surface_state_ = OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT;
 
   if (did_create_and_initialize_first_output_surface_) {
     // TODO(boliu): See if we can remove this when impl-side painting is always
     // on. Does anything on the main thread need to update after recreate?
     needs_commit_ = true;
@@ skipping 29 matching lines @@
       static_cast<int>(begin_impl_frame_state_),
       static_cast<int>(commit_state_),
       has_pending_tree_ ? 'T' : 'F',
       pending_tree_is_ready_for_activation_ ? 'T' : 'F',
       active_tree_needs_first_draw_ ? 'T' : 'F',
       max_pending_swaps_,
       pending_swaps_);
 }
 
 }  // namespace cc