Enable BeginFrame scheduling on aura

content/browser/renderer_host/begin_frame_observer_proxy.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/begin_frame_observer_proxy.h"
 
 namespace content {
 
 BeginFrameObserverProxy::BeginFrameObserverProxy(
     BeginFrameObserverProxyClient* client)
     : needs_begin_frames_(false),
       client_(client),
       compositor_(nullptr) {
 }
 
 BeginFrameObserverProxy::~BeginFrameObserverProxy() {
+  ResetCompositor();
 }
 
 void BeginFrameObserverProxy::SetNeedsBeginFrames(bool needs_begin_frames) {
   if (needs_begin_frames_ == needs_begin_frames)
     return;
 
   needs_begin_frames_ = needs_begin_frames;
 
   // In some cases, BeginFrame message is requested before |client_|'s window is
   // added in the root window hierarchy.
   if (!compositor_)
     return;
 
   if (needs_begin_frames)
     StartObservingBeginFrames();
   else
     StopObservingBeginFrames();
 }
 
 void BeginFrameObserverProxy::SetCompositor(ui::Compositor* compositor) {
   DCHECK(!compositor_);
-  DCHECK(compositor);
+
+  if (!compositor)

[simonhong, 2015/03/27 17:37:54]

I found that when RWHV is destroyed it calls SetCompositor() with null pointer.
So, I added this like DelegatedFrameHost does.

[danakj, 2015/03/27 17:41:47]

I don't think we should have SetCompositor(nullptr) and ResetCompositor. We
should change it to call ResetCompositor (for both cases).

+    return;
 
   compositor_ = compositor;
+  compositor_->AddObserver(this);
   if (needs_begin_frames_)
     StartObservingBeginFrames();
 }
 
 void BeginFrameObserverProxy::ResetCompositor() {
   if (!compositor_)
     return;
+  compositor_->RemoveObserver(this);
 
   if (needs_begin_frames_)
     StopObservingBeginFrames();
   compositor_ = nullptr;
 }
 
 void BeginFrameObserverProxy::OnSendBeginFrame(const cc::BeginFrameArgs& args) {
   if (last_sent_begin_frame_args_.frame_time != args.frame_time)
     client_->SendBeginFrame(args);
   last_sent_begin_frame_args_ = args;
 }
 
+void BeginFrameObserverProxy::OnCompositingShuttingDown(
+    ui::Compositor* compositor) {
+  ResetCompositor();
+}
+
 void BeginFrameObserverProxy::StartObservingBeginFrames() {
   DCHECK(compositor_);
   compositor_->AddBeginFrameObserver(this);
 }
 
 void BeginFrameObserverProxy::StopObservingBeginFrames() {
   DCHECK(compositor_);
   compositor_->RemoveBeginFrameObserver(this);
 }
 
 }  // namespace content