cc: Create ProxyBeginFrameSource

cc/scheduler/begin_frame_source.cc

Index: cc/scheduler/begin_frame_source.cc
diff --git a/cc/scheduler/begin_frame_source.cc b/cc/scheduler/begin_frame_source.cc
index c245bd63fc380e855ed3f1ff7457376690713bf1..9676e2498edf5693269aa1f53572d087a1b7ff9e 100644
--- a/cc/scheduler/begin_frame_source.cc
+++ b/cc/scheduler/begin_frame_source.cc
@@ -137,6 +137,52 @@ void BeginFrameSourceMixIn::AsValueInto(base::debug::TracedValue* dict) const {
   dict->SetBoolean("needs_begin_frames", NeedsBeginFrames());
 }
 
+// ProxyBeginFrameSource
+ProxyBeginFrameSource::ProxyBeginFrameSource() : delegate_(nullptr) {
+}
+
+ProxyBeginFrameSource::~ProxyBeginFrameSource() {
+  DCHECK(!observer_list_.might_have_observers());
+}
+
+bool ProxyBeginFrameSource::NeedsBeginFrames() const {
+  return observer_list_.might_have_observers();
+}
+
+void ProxyBeginFrameSource::AddObserver(BeginFrameObserver* obs) {
+  // If |missed_begin_frame_args_| is still effective, send it to the new
+  // |obs| immediately.
+  if (!obs->LastUsedBeginFrameArgs().deadline.is_null() &&
+      obs->LastUsedBeginFrameArgs() != missed_begin_frame_args_) {
+    missed_begin_frame_args_.type = BeginFrameArgs::MISSED;
+    obs->OnBeginFrame(missed_begin_frame_args_);
+  }
+
+  if (!observer_list_.might_have_observers() && delegate_)
+    delegate_->SetChildrenNeedBeginFrames(true);
+  observer_list_.AddObserver(obs);
+}
+
+void ProxyBeginFrameSource::RemoveObserver(BeginFrameObserver* obs) {
+  DCHECK(observer_list_.HasObserver(obs));
+  observer_list_.RemoveObserver(obs);
+
+  if (!observer_list_.might_have_observers() && delegate_)
+    delegate_->SetChildrenNeedBeginFrames(false);
+}
+
+void ProxyBeginFrameSource::AsValueInto(base::debug::TracedValue* dict) const {
+  dict->SetString("type", "ProxyBeginFrameSource");
+  dict->SetBoolean("has_observers", observer_list_.might_have_observers());
+}
+
+void ProxyBeginFrameSource::BeginFrames(const BeginFrameArgs& args) {
+  FOR_EACH_OBSERVER(BeginFrameObserver,
+                    observer_list_,
+                    OnBeginFrame(args));
+  missed_begin_frame_args_ = args;
+}
+
 // BackToBackBeginFrameSourceMixIn --------------------------------------------
 scoped_ptr<BackToBackBeginFrameSource> BackToBackBeginFrameSource::Create(
     base::SingleThreadTaskRunner* task_runner) {