cc: Use multiple PrepareTiles approaches

cc/scheduler/scheduler_state_machine.h

Index: cc/scheduler/scheduler_state_machine.h
diff --git a/cc/scheduler/scheduler_state_machine.h b/cc/scheduler/scheduler_state_machine.h
index cf29ca9b6a53ec89a43c1b20e905e9c4792dff8f..f73b7e894ca2df8d46fc8f913557053c9ac1d7d2 100644
--- a/cc/scheduler/scheduler_state_machine.h
+++ b/cc/scheduler/scheduler_state_machine.h
@@ -67,6 +67,7 @@ class CC_EXPORT SchedulerStateMachine {
     BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE,
     BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR,
     BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE,
+    BEGIN_IMPL_FRAME_DEADLINE_MODE_TRY_TO_AVOID_CHECKERBOARD,
     BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW,
   };
   static const char* BeginImplFrameDeadlineModeToString(
@@ -82,14 +83,36 @@ class CC_EXPORT SchedulerStateMachine {
   };
   static const char* CommitStateToString(CommitState state);
 
-  enum ForcedRedrawOnTimeoutState {
-    FORCED_REDRAW_STATE_IDLE,
-    FORCED_REDRAW_STATE_WAITING_FOR_COMMIT,
-    FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION,
-    FORCED_REDRAW_STATE_WAITING_FOR_DRAW,
+  enum PrepareTilesApproach {
+    // This approach calls PrepareTiles after every commit and after draws if
+    // there wasn't a commit for that frame. With this approach, we cannot trust
+    // NotifyReadyToActivate and NotifyReadyToDraw and they should only be used
+    // as hints. All other approaches have trustworthy NotifyReadyToActivate's
+    // and NotifyReadyToDraw's.
+    PREPARE_TILES_APPROACH_PRIORITIZE_LATENCY,
+    // This approach only calls PrepareTiles at the start of a frame so new
+    // active tree work starts ASAP, but the pending tree work doesn't.
+    PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_WORK,
+    // This approach calls PrepareTiles at the start of every frame and after
+    // every commit so any new work starts ASAP.
+    PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_PENDING_WORK,
+    // This approach calls PrepareTiles at the start of every frame, after every
+    // commit, and after every activation so any new or canceled work is
+    // reflected immediately.
+    PREPARE_TILES_APPROACH_ACCURATE_ACTIVE_PENDING_CANCELED_WORK,
   };
-  static const char* ForcedRedrawOnTimeoutStateToString(
-      ForcedRedrawOnTimeoutState state);
+  static const char* PrepareTilesApproachToString(
+      PrepareTilesApproach approach);
+
+  enum PrepareTilesReason {
+    PREPARE_TILES_NOT_NEEDED,
+    PREPARE_TILES_REQUESTED,
+    PREPARE_TILES_NEEDED_FOR_COMMIT,
+    PREPARE_TILES_NEEDED_FOR_ACTIVATION,
+    PREPARE_TILES_NEEDED_FOR_ABORTED_DRAW,
+    PREPARE_TILES_NEEDED_TO_EVICT_TILES,
+  };
+  static const char* PrepareTilesReasonToString(PrepareTilesReason reason);
 
   bool CommitPending() const {
     return commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_SENT ||
@@ -99,7 +122,9 @@ class CC_EXPORT SchedulerStateMachine {
   CommitState commit_state() const { return commit_state_; }
 
   bool RedrawPending() const { return needs_redraw_; }
-  bool PrepareTilesPending() const { return needs_prepare_tiles_; }
+  bool PrepareTilesPending() const {
+    return prepare_tiles_reason_ != PREPARE_TILES_NOT_NEEDED;
+  }
 
   enum Action {
     ACTION_NONE,
@@ -126,6 +151,10 @@ class CC_EXPORT SchedulerStateMachine {
   // to make progress.
   bool BeginFrameNeeded() const;
 
+  // This reflects the actual state of the BeginFrameSource, not just whether
+  // the SchedulerStateMachine wants BeginFrames at this instance.
+  void NotifyBeginFrameSourceActive(bool active);
+
   // Indicates that the system has entered and left a BeginImplFrame callback.
   // The scheduler will not draw more than once in a given BeginImplFrame
   // callback nor send more than one BeginMainFrame message.
@@ -159,7 +188,7 @@ class CC_EXPORT SchedulerStateMachine {
 
   // Indicates that prepare-tiles is required. This guarantees another
   // PrepareTiles will occur shortly (even if no redraw is required).
-  void SetNeedsPrepareTiles();
+  void SetNeedsPrepareTiles(bool for_commit);
 
   // Make deadline wait for ReadyToDraw signal.
   void SetWaitForReadyToDraw();
@@ -186,8 +215,8 @@ class CC_EXPORT SchedulerStateMachine {
     return impl_latency_takes_priority_;
   }
 
-  // Indicates whether ACTION_DRAW_AND_SWAP_IF_POSSIBLE drew to the screen.
-  void DidDrawIfPossibleCompleted(DrawResult result);
+  // Indicates whether a draw request succeeded or not.
+  void SetDrawResult(DrawResult result);
 
   // Indicates that a new commit flow needs to be performed, either to pull
   // updates from the main thread to the impl, or to push deltas from the impl
@@ -224,12 +253,14 @@ class CC_EXPORT SchedulerStateMachine {
   // Indicates the active tree's visible tiles are ready to be drawn.
   void NotifyReadyToDraw();
 
+  // Indicates we shouldn't draw the active tree until we won't checkerboard.
+  void SetRequiresHighResToDraw(bool required);
+
   bool has_pending_tree() const { return has_pending_tree_; }
   bool active_tree_needs_first_draw() const {
     return active_tree_needs_first_draw_;
   }
 
-  void DidPrepareTiles();
   void DidLoseOutputSurface();
   void DidCreateAndInitializeOutputSurface();
   bool HasInitializedOutputSurface() const;
@@ -291,7 +322,8 @@ class CC_EXPORT SchedulerStateMachine {
   OutputSurfaceState output_surface_state_;
   BeginImplFrameState begin_impl_frame_state_;
   CommitState commit_state_;
-  ForcedRedrawOnTimeoutState forced_redraw_state_;
+  PrepareTilesApproach prepare_tiles_approach_;
+  PrepareTilesReason prepare_tiles_reason_;
 
   // These are used for tracing only.
   int commit_count_;
@@ -308,25 +340,27 @@ class CC_EXPORT SchedulerStateMachine {
   bool request_swap_funnel_;
   bool send_begin_main_frame_funnel_;
   bool invalidate_output_surface_funnel_;
+  // TODO(brianderson): Update the comment below.
   // prepare_tiles_funnel_ is "filled" each time PrepareTiles is called
   // and "drained" on each BeginImplFrame. If the funnel gets too full,
   // we start throttling ACTION_PREPARE_TILES such that we average one
   // PrepareTiles per BeginImplFrame.
   int prepare_tiles_funnel_;
 
-  int consecutive_checkerboard_animations_;
   int max_pending_swaps_;
   int pending_swaps_;
   bool needs_redraw_;
+  DrawResult last_draw_result_;
   bool needs_animate_;
-  bool needs_prepare_tiles_;
   bool needs_commit_;
   bool visible_;
   bool can_start_;
   bool can_draw_;
   bool has_pending_tree_;
   bool pending_tree_is_ready_for_activation_;
+  bool requires_high_res_to_draw_;
   bool active_tree_needs_first_draw_;
+  bool active_tree_ready_to_draw_;
   bool did_create_and_initialize_first_output_surface_;
   bool impl_latency_takes_priority_;
   bool skip_next_begin_main_frame_to_reduce_latency_;