cc: Plumbing for BeginFrameSource based on Surfaces

cc/surfaces/surface.cc

Index: cc/surfaces/surface.cc
diff --git a/cc/surfaces/surface.cc b/cc/surfaces/surface.cc
index 16987cb84e49b356bd2cf4afa0fd255f9ddf82a6..11ff12f7f2fe46f1756ebcc5b177c3513141924e 100644
--- a/cc/surfaces/surface.cc
+++ b/cc/surfaces/surface.cc
@@ -35,6 +35,9 @@ Surface::~Surface() {
   }
   if (!draw_callback_.is_null())
     draw_callback_.Run(SurfaceDrawStatus::DRAW_SKIPPED);
+
+  if (factory_)
+    factory_->SetBeginFrameSource(surface_id_, NULL);
 }
 
 void Surface::QueueFrame(scoped_ptr<CompositorFrame> frame,
@@ -164,6 +167,33 @@ void Surface::SatisfyDestructionDependencies(
       destruction_dependencies_.end());
 }
 
+void Surface::AddBeginFrameSource(BeginFrameSource* begin_frame_source) {
+  DCHECK(base::STLIsSorted(begin_frame_sources_));
+  DCHECK(!ContainsValue(begin_frame_sources_, begin_frame_source));
+  begin_frame_sources_.insert(begin_frame_source);
+  UpdatePrimaryBeginFrameSource();
+}
+
+void Surface::RemoveBeginFrameSource(BeginFrameSource* begin_frame_source) {
+  size_t erase_count = begin_frame_sources_.erase(begin_frame_source);
+  DCHECK_EQ(1u, erase_count);
+  UpdatePrimaryBeginFrameSource();
+}
+
+void Surface::UpdatePrimaryBeginFrameSource() {
+  // Ensure the BeginFrameSources are sorted so our we make a stable decision
+  // regarding which source is primary.
+  // TODO(brianderson): Do something smarter based on coverage instead.
+  DCHECK(base::STLIsSorted(begin_frame_sources_));
+
+  BeginFrameSource* primary_source = nullptr;
+  if (!begin_frame_sources_.empty())
+    primary_source = *begin_frame_sources_.begin();
+
+  if (factory_)
+    factory_->SetBeginFrameSource(surface_id_, primary_source);
+}
+
 void Surface::ClearCopyRequests() {
   if (current_frame_) {
     for (const auto& render_pass :