Hook up ui::Compositor to Display's BeginFrameSource

cc/trees/single_thread_proxy.cc

 // Copyright 2011 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 "cc/trees/single_thread_proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/animation/animation_events.h"
@@ skipping 471 matching lines @@
     // TODO(brianderson): We should not be receiving 0 intervals.
     interval = BeginFrameArgs::DefaultInterval();
   }
 
   last_vsync_timebase_ = timebase;
 
   if (synthetic_begin_frame_source_)
     synthetic_begin_frame_source_->OnUpdateVSyncParameters(timebase, interval);
 }
 
+void SingleThreadProxy::SetBeginFrameSource(BeginFrameSource* source) {
+  // This should only happen when using the scheduler.
+  DCHECK(layer_tree_host_->settings().single_thread_proxy_scheduler);
+  // TODO(enne): this overrides any preexisting begin frame source.  Those

[no sievers, 2016/03/25 18:55:08]

Yea see other comment wrt Android. Since it currently uses
|external_begin_frame_source| there, one would probably override the other. But
it's probably straightforward to just have them both use the same source now.

+  // other sources will eventually be removed and this will be the only path.
+  scheduler_on_impl_thread_->SetBeginFrameSource(source);
+}
+
 void SingleThreadProxy::SetEstimatedParentDrawTime(base::TimeDelta draw_time) {
   if (scheduler_on_impl_thread_)
     scheduler_on_impl_thread_->SetEstimatedParentDrawTime(draw_time);
 }
 
 void SingleThreadProxy::DidSwapBuffersOnImplThread() {
   TRACE_EVENT0("cc", "SingleThreadProxy::DidSwapBuffersOnImplThread");
   if (scheduler_on_impl_thread_)
     scheduler_on_impl_thread_->DidSwapBuffers();
   client_->DidPostSwapBuffers();
@@ skipping 395 matching lines @@
       << "DidFinishImplFrame called while not inside an impl frame!";
   inside_impl_frame_ = false;
 #endif
 }
 
 void SingleThreadProxy::SendBeginFramesToChildren(const BeginFrameArgs& args) {
   layer_tree_host_->SendBeginFramesToChildren(args);
 }
 
 }  // namespace cc