cc: Make scheduling be driven by vsync for android webview.

cc/scheduler/scheduler_state_machine.cc

Index: cc/scheduler/scheduler_state_machine.cc
diff --git a/cc/scheduler/scheduler_state_machine.cc b/cc/scheduler/scheduler_state_machine.cc
index c2d0ba294b8ef2baa17389e3de7b92cfeadc078e..62b49cc5923ae2e533435fc204d622d897cac317 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -26,10 +26,12 @@ SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
       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),
       perform_swap_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),
@@ -38,7 +40,6 @@ SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
       needs_animate_(false),
       needs_prepare_tiles_(false),
       needs_commit_(false),
-      inside_poll_for_anticipated_draw_triggers_(false),
       visible_(false),
       can_start_(false),
       can_draw_(false),
@@ -88,6 +89,22 @@ const char* SchedulerStateMachine::BeginImplFrameStateToString(
   return "???";
 }
 
+const char* SchedulerStateMachine::BeginImplFrameDeadlineModeToString(
+    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";
+  }
+  NOTREACHED();
+  return "???";
+}
+
 const char* SchedulerStateMachine::CommitStateToString(CommitState state) {
   switch (state) {
     case COMMIT_STATE_IDLE:
@@ -145,6 +162,8 @@ const char* SchedulerStateMachine::ActionToString(Action action) {
       return "ACTION_BEGIN_OUTPUT_SURFACE_CREATION";
     case ACTION_PREPARE_TILES:
       return "ACTION_PREPARE_TILES";
+    case ACTION_INVALIDATE_OUTPUT_SURFACE:
+      return "ACTION_INVALIDATE_OUTPUT_SURFACE";
   }
   NOTREACHED();
   return "???";
@@ -188,6 +207,8 @@ void SchedulerStateMachine::AsValueInto(
   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_);
@@ -220,23 +241,6 @@ void SchedulerStateMachine::AsValueInto(
   state->EndDictionary();
 }
 
-void SchedulerStateMachine::AdvanceCurrentFrameNumber() {
-  current_frame_number_++;
-
-  animate_funnel_ = false;
-  perform_swap_funnel_ = false;
-  request_swap_funnel_ = false;
-  send_begin_main_frame_funnel_ = false;
-
-  // "Drain" the PrepareTiles funnel.
-  if (prepare_tiles_funnel_ > 0)
-    prepare_tiles_funnel_--;
-
-  skip_begin_main_frame_to_reduce_latency_ =
-      skip_next_begin_main_frame_to_reduce_latency_;
-  skip_next_begin_main_frame_to_reduce_latency_ = false;
-}
-
 bool SchedulerStateMachine::PendingDrawsShouldBeAborted() const {
   // These are all the cases where we normally cannot or do not want to draw
   // but, if needs_redraw_ is true and we do not draw to make forward progress,
@@ -461,14 +465,30 @@ bool SchedulerStateMachine::ShouldPrepareTiles() const {
     return false;
 
   // Limiting to once per-frame is not enough, since we only want to
-  // prepare tiles _after_ draws. Polling for draw triggers and
-  // begin-frame are mutually exclusive, so we limit to these two cases.
-  if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE &&
-      !inside_poll_for_anticipated_draw_triggers_)
+  // prepare tiles _after_ draws.
+  if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
     return false;
+
   return needs_prepare_tiles_;
 }
 
+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 or inside deadline.
+  if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING &&
+      begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
+    return false;
+
+  return needs_redraw_ || needs_prepare_tiles_;
+}
+
 SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
   if (ShouldActivatePendingTree())
     return ACTION_ACTIVATE_SYNC_TREE;
@@ -488,6 +508,8 @@ SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
     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;
@@ -503,25 +525,11 @@ void SchedulerStateMachine::UpdateState(Action action) {
       return;
 
     case ACTION_ANIMATE:
-      DCHECK(!animate_funnel_);
-      last_frame_number_animate_performed_ = current_frame_number_;
-      animate_funnel_ = true;
-      needs_animate_ = false;
-      // TODO(skyostil): Instead of assuming this, require the client to tell
-      // us.
-      SetNeedsRedraw();
+      UpdateStateOnAnimate();
       return;
 
     case ACTION_SEND_BEGIN_MAIN_FRAME:
-      DCHECK(!has_pending_tree_ ||
-             settings_.main_frame_before_activation_enabled);
-      DCHECK(visible_);
-      DCHECK(!send_begin_main_frame_funnel_);
-      commit_state_ = COMMIT_STATE_BEGIN_MAIN_FRAME_SENT;
-      needs_commit_ = false;
-      send_begin_main_frame_funnel_ = true;
-      last_frame_number_begin_main_frame_sent_ =
-          current_frame_number_;
+      UpdateStateOnSendBeginMainFrame();
       return;
 
     case ACTION_COMMIT: {
@@ -544,23 +552,39 @@ void SchedulerStateMachine::UpdateState(Action action) {
     }
 
     case ACTION_BEGIN_OUTPUT_SURFACE_CREATION:
-      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);
-      DCHECK(!has_pending_tree_);
-      DCHECK(!active_tree_needs_first_draw_);
+      UpdateStateOnBeginOutputSurfaceCreation();
       return;
 
     case ACTION_PREPARE_TILES:
       UpdateStateOnPrepareTiles();
       return;
+
+    case ACTION_INVALIDATE_OUTPUT_SURFACE:
+      UpdateStateOnInvalidateOutputSurface();
+      return;
   }
 }
 
+void SchedulerStateMachine::UpdateStateOnAnimate() {
+  DCHECK(!animate_funnel_);
+  last_frame_number_animate_performed_ = current_frame_number_;
+  animate_funnel_ = true;
+  needs_animate_ = false;
+  // TODO(skyostil): Instead of assuming this, require the client to tell
+  // us.
+  SetNeedsRedraw();
+}
+
+void SchedulerStateMachine::UpdateStateOnSendBeginMainFrame() {
+  DCHECK(!has_pending_tree_ || settings_.main_frame_before_activation_enabled);
+  DCHECK(visible_);
+  DCHECK(!send_begin_main_frame_funnel_);
+  commit_state_ = COMMIT_STATE_BEGIN_MAIN_FRAME_SENT;
+  needs_commit_ = false;
+  send_begin_main_frame_funnel_ = true;
+  last_frame_number_begin_main_frame_sent_ = current_frame_number_;
+}
+
 void SchedulerStateMachine::UpdateStateOnCommit(bool commit_has_no_updates) {
   commit_count_++;
 
@@ -655,6 +679,28 @@ void SchedulerStateMachine::UpdateStateOnPrepareTiles() {
   needs_prepare_tiles_ = false;
 }
 
+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);
+  DCHECK(!has_pending_tree_);
+  DCHECK(!active_tree_needs_first_draw_);
+}
+
+void SchedulerStateMachine::UpdateStateOnInvalidateOutputSurface() {
+  DCHECK(!invalidate_output_surface_funnel_);
+  invalidate_output_surface_funnel_ = true;
+  last_frame_number_invalidate_output_surface_performed_ =
+      current_frame_number_;
+  // There is no guarantee that a draw will arrive from the synchronous
+  // compositor. We clear this flag here so that the pipeline isn't blocked.
+  active_tree_needs_first_draw_ = false;
+}
+
 void SchedulerStateMachine::SetSkipNextBeginMainFrameToReduceLatency() {
   TRACE_EVENT_INSTANT0("cc",
                        "Scheduler: SkipNextBeginMainFrameToReduceLatency",
@@ -674,44 +720,8 @@ bool SchedulerStateMachine::BeginFrameNeeded() const {
   // TODO(brianderson): Support output surface creation inside a BeginFrame.
   if (!HasInitializedOutputSurface())
     return false;
-
-  if (SupportsProactiveBeginFrame()) {
-    return (BeginFrameNeededToAnimateOrDraw() ||
-            BeginFrameNeededForChildren() ||
-            ProactiveBeginFrameWanted());
-  }
-
-  // Proactive BeginFrames are bad for the synchronous compositor because we
-  // have to draw when we get the BeginFrame and could end up drawing many
-  // duplicate frames if our new frame isn't ready in time.
-  // To poll for state with the synchronous compositor without having to draw,
-  // we rely on ShouldPollForAnticipatedDrawTriggers instead.
-  // Synchronous compositor doesn't have a browser.
-  DCHECK(!children_need_begin_frames_);
-  return BeginFrameNeededToAnimateOrDraw();
-}
-
-bool SchedulerStateMachine::ShouldPollForAnticipatedDrawTriggers() const {
-  // ShouldPollForAnticipatedDrawTriggers is what we use in place of
-  // ProactiveBeginFrameWanted when we are using the synchronous
-  // compositor.
-  if (!SupportsProactiveBeginFrame()) {
-    return !BeginFrameNeededToAnimateOrDraw() && ProactiveBeginFrameWanted();
-  }
-
-  // Non synchronous compositors should rely on
-  // ProactiveBeginFrameWanted to poll for state instead.
-  return false;
-}
-
-// Note: If SupportsProactiveBeginFrame is false, the scheduler should poll
-// for changes in it's draw state so it can request a BeginFrame when it's
-// actually ready.
-bool SchedulerStateMachine::SupportsProactiveBeginFrame() const {
-  // It is undesirable to proactively request BeginFrames if we are
-  // using a synchronous compositor because we *must* draw for every
-  // BeginFrame, which could cause duplicate draws.
-  return !settings_.using_synchronous_renderer_compositor;
+  return (BeginFrameNeededToAnimateOrDraw() || BeginFrameNeededForChildren() ||
+          ProactiveBeginFrameWanted());
 }
 
 void SchedulerStateMachine::SetChildrenNeedBeginFrames(
@@ -770,34 +780,49 @@ bool SchedulerStateMachine::ProactiveBeginFrameWanted() const {
 }
 
 void SchedulerStateMachine::OnBeginImplFrame() {
-  AdvanceCurrentFrameNumber();
-  DCHECK_EQ(begin_impl_frame_state_, BEGIN_IMPL_FRAME_STATE_IDLE)
-      << AsValue()->ToString();
   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING;
+
+  current_frame_number_++;
+
+  // Clear funnels for any actions we perform during the frame.
+  animate_funnel_ = false;
+  perform_swap_funnel_ = false;
+  request_swap_funnel_ = false;
+  send_begin_main_frame_funnel_ = false;
+  invalidate_output_surface_funnel_ = false;
+
+  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() {
-  DCHECK_EQ(begin_impl_frame_state_,
-            BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING)
-      << AsValue()->ToString();
   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME;
 }
 
 void SchedulerStateMachine::OnBeginImplFrameDeadline() {
-  DCHECK_EQ(begin_impl_frame_state_, BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME)
-      << AsValue()->ToString();
   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE;
+
+  // Clear funnels for any actions we perform during the deadline.
+  perform_swap_funnel_ = false;
+  request_swap_funnel_ = false;
+  invalidate_output_surface_funnel_ = false;
+
+  // "Drain" the PrepareTiles funnel.
+  if (prepare_tiles_funnel_ > 0)
+    prepare_tiles_funnel_--;
 }
 
 void SchedulerStateMachine::OnBeginImplFrameIdle() {
-  DCHECK_EQ(begin_impl_frame_state_, BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
-      << AsValue()->ToString();
   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_IDLE;
 }
 
 SchedulerStateMachine::BeginImplFrameDeadlineMode
 SchedulerStateMachine::CurrentBeginImplFrameDeadlineMode() const {
-  if (ShouldTriggerBeginImplFrameDeadlineImmediately()) {
+  if (settings_.using_synchronous_renderer_compositor) {
+    // No deadline for synchronous compositor.
+    return BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE;
+  } 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
@@ -815,7 +840,6 @@ SchedulerStateMachine::CurrentBeginImplFrameDeadlineMode() const {
 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;
 
@@ -890,15 +914,6 @@ bool SchedulerStateMachine::MainThreadIsInHighLatencyMode() const {
   return active_tree_needs_first_draw_;
 }
 
-void SchedulerStateMachine::DidEnterPollForAnticipatedDrawTriggers() {
-  AdvanceCurrentFrameNumber();
-  inside_poll_for_anticipated_draw_triggers_ = true;
-}
-
-void SchedulerStateMachine::DidLeavePollForAnticipatedDrawTriggers() {
-  inside_poll_for_anticipated_draw_triggers_ = false;
-}
-
 void SchedulerStateMachine::SetVisible(bool visible) { visible_ = visible; }
 
 void SchedulerStateMachine::SetCanDraw(bool can_draw) { can_draw_ = can_draw; }