[exo]CompositorFrameSinkHolder calls WillDraw in DidReceiveCompositorFrameAck

CommitSurfaceHierarchy() moves pending_frame_callbacks_ into
frame_callbacks_ before calling UpdateSurface() so that the ack doesn't
arrive too early.

exo::Surface is the only class which needs
MojoCompositorFrameSinkClient::WillDrawSurface(). With this change, we
can remove WillDrawSurface from the mojo interface and reduce IPC overhead.

BUG=671202, 709076

Review-Url: https://codereview.chromium.org/2786643002
Cr-Commit-Position: refs/heads/master@{#462678}

components/exo/compositor_frame_sink_holder.cc

@@ -41,7 +41,8 @@ void CompositorFrameSinkHolder::SetResourceReleaseCallback(
 // cc::mojom::MojoCompositorFrameSinkClient overrides:
 
 void CompositorFrameSinkHolder::DidReceiveCompositorFrameAck() {
-  // TODO(staraz): Implement this
+  if (surface_)
+    surface_->DidReceiveCompositorFrameAck();
 }
 
 void CompositorFrameSinkHolder::OnBeginFrame(const cc::BeginFrameArgs& args) {
@@ -62,10 +63,7 @@ void CompositorFrameSinkHolder::ReclaimResources(
 
 void CompositorFrameSinkHolder::WillDrawSurface(
     const cc::LocalSurfaceId& local_surface_id,
-    const gfx::Rect& damage_rect) {
-  if (surface_)
-    surface_->WillDraw();
-}
+    const gfx::Rect& damage_rect) {}
 
 ////////////////////////////////////////////////////////////////////////////////
 // cc::ExternalBeginFrameSourceClient overrides:

components/exo/surface.cc

@@ -464,6 +464,13 @@ void Surface::CommitSurfaceHierarchy() {
     local_surface_id_ = id_allocator_.GenerateId();
   }
 
+  // Move pending frame callbacks to the end of frame_callbacks_.
+  frame_callbacks_.splice(frame_callbacks_.end(), pending_frame_callbacks_);
+
+  // Move pending presentation callbacks to the end of presentation_callbacks_.
+  presentation_callbacks_.splice(presentation_callbacks_.end(),
+                                 pending_presentation_callbacks_);
+
   UpdateSurface(false);
 
   if (old_local_surface_id != local_surface_id_) {
@@ -492,13 +499,6 @@ void Surface::CommitSurfaceHierarchy() {
          compositor_frame_sink_holder_->HasReleaseCallbackForResource(
              current_resource_.id));
 
-  // Move pending frame callbacks to the end of frame_callbacks_.
-  frame_callbacks_.splice(frame_callbacks_.end(), pending_frame_callbacks_);
-
-  // Move pending presentation callbacks to the end of presentation_callbacks_.
-  presentation_callbacks_.splice(presentation_callbacks_.end(),
-                                 pending_presentation_callbacks_);
-
   // Synchronize window hierarchy. This will position and update the stacking
   // order of all sub-surfaces after committing all pending state of sub-surface
   // descendants.
@@ -605,7 +605,7 @@ std::unique_ptr<base::trace_event::TracedValue> Surface::AsTracedValue() const {
   return value;
 }
 
-void Surface::WillDraw() {
+void Surface::DidReceiveCompositorFrameAck() {
   active_frame_callbacks_.splice(active_frame_callbacks_.end(),
                                  frame_callbacks_);
   swapping_presentation_callbacks_.splice(

components/exo/surface.h

@@ -191,8 +191,9 @@ class Surface : public ui::ContextFactoryObserver,
   // Returns a trace value representing the state of the surface.
   std::unique_ptr<base::trace_event::TracedValue> AsTracedValue() const;
 
-  // Call this to indicate that surface is being scheduled for a draw.
-  void WillDraw();
+  // Call this to indicate that the previous CompositorFrame is processed and
+  // the surface is being scheduled for a draw.
+  void DidReceiveCompositorFrameAck();
 
   // Called when the begin frame source has changed.
   void SetBeginFrameSource(cc::BeginFrameSource* begin_frame_source);

components/exo/surface_unittest.cc

@@ -329,8 +329,9 @@ TEST_F(SurfaceTest, SendsBeginFrameAcks) {
   surface->Commit();  // Move callback from pending callbacks to current ones.
   RunAllPendingInMessageLoop();
 
-  // Surface should add itself as observer during WillDraw().
-  surface->WillDraw();
+  // Surface should add itself as observer during
+  // DidReceiveCompositorFrameAck().
+  surface->DidReceiveCompositorFrameAck();
   EXPECT_EQ(1u, source.num_observers());
 
   cc::BeginFrameArgs args(source.CreateBeginFrameArgs(BEGINFRAME_FROM_HERE));