[exo] Clean up BeginFrame distribution & add acks in Surface.

components/exo/surface.cc

Index: components/exo/surface.cc
diff --git a/components/exo/surface.cc b/components/exo/surface.cc
index be4b90ba2d34b2b99d34a99c847e10480a2183ca..bdcd746536ddccae9d57dc5d578742f4868d6c1b 100644
--- a/components/exo/surface.cc
+++ b/components/exo/surface.cc
@@ -432,6 +432,13 @@ void Surface::Commit() {
     CheckIfSurfaceHierarchyNeedsCommitToNewSurfaces();
     CommitSurfaceHierarchy();
   }
+
+  if (begin_frame_source_ && current_begin_frame_ack_.sequence_number !=
+                                 cc::BeginFrameArgs::kInvalidFrameNumber) {
+    begin_frame_source_->DidFinishFrame(this, current_begin_frame_ack_);
+    current_begin_frame_ack_.sequence_number =
+        cc::BeginFrameArgs::kInvalidFrameNumber;
+  }
 }
 
 void Surface::CommitSurfaceHierarchy() {
@@ -603,17 +610,42 @@ void Surface::WillDraw() {
                                  frame_callbacks_);
   swapping_presentation_callbacks_.splice(
       swapping_presentation_callbacks_.end(), presentation_callbacks_);
+  UpdateNeedsBeginFrame();
+}
+
+void Surface::SetBeginFrameSource(cc::BeginFrameSource* begin_frame_source) {
+  if (needs_begin_frame_) {
+    DCHECK(begin_frame_source_);
+    begin_frame_source_->RemoveObserver(this);
+    needs_begin_frame_ = false;
+  }
+  begin_frame_source_ = begin_frame_source;
+  UpdateNeedsBeginFrame();
 }
 
-bool Surface::NeedsBeginFrame() const {
-  return !active_frame_callbacks_.empty();
+void Surface::UpdateNeedsBeginFrame() {
+  if (!begin_frame_source_)
+    return;
+
+  bool needs_begin_frame = !active_frame_callbacks_.empty();
+  if (needs_begin_frame == needs_begin_frame_)
+    return;
+
+  needs_begin_frame_ = needs_begin_frame;
+  if (needs_begin_frame_)
+    begin_frame_source_->AddObserver(this);
+  else
+    begin_frame_source_->RemoveObserver(this);
 }
 
-void Surface::BeginFrame(base::TimeTicks frame_time) {
+bool Surface::OnBeginFrameDerivedImpl(const cc::BeginFrameArgs& args) {
+  current_begin_frame_ack_ = cc::BeginFrameAck(
+      args.source_id, args.sequence_number, args.sequence_number, 0, false);
   while (!active_frame_callbacks_.empty()) {
-    active_frame_callbacks_.front().Run(frame_time);
+    active_frame_callbacks_.front().Run(args.frame_time);
     active_frame_callbacks_.pop_front();
   }
+  return true;
 }
 
 void Surface::CheckIfSurfaceHierarchyNeedsCommitToNewSurfaces() {
@@ -806,6 +838,9 @@ void Surface::UpdateSurface(bool full_damage) {
   quad_state->opacity = state_.alpha;
 
   cc::CompositorFrame frame;
+  current_begin_frame_ack_.has_damage = true;
+  frame.metadata.begin_frame_ack = current_begin_frame_ack_;
+
   if (current_resource_.id) {
     // Texture quad is only needed if buffer is not fully transparent.
     if (state_.alpha) {