cc:: Change plumbing for external_begin_frame_source to the Scheduler.

cc/test/fake_proxy.h

 // Copyright 2012 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.
 
 #ifndef CC_TEST_FAKE_PROXY_H_
 #define CC_TEST_FAKE_PROXY_H_
 
 #include "base/single_thread_task_runner.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/proxy.h"
@@ skipping 17 matching lines @@
   void SetNeedsAnimate() override {}
   void SetNeedsUpdateLayers() override {}
   void SetNeedsCommit() override {}
   void SetNeedsRedraw(const gfx::Rect& damage_rect) override {}
   void SetNextCommitWaitsForActivation() override {}
   void NotifyInputThrottledUntilCommit() override {}
   void SetDeferCommits(bool defer_commits) override {}
   void MainThreadHasStoppedFlinging() override {}
   bool BeginMainFrameRequested() const override;
   bool CommitRequested() const override;
-  void Start() override {}
+  void Start(
+      scoped_ptr<BeginFrameSource> external_begin_frame_source) override {}
   void Stop() override {}
   bool SupportsImplScrolling() const override;
   bool MainFrameWillHappenForTesting() override;
   void SetChildrenNeedBeginFrames(bool children_need_begin_frames) override {}
   void SetAuthoritativeVSyncInterval(const base::TimeDelta& interval) override {
   }
   void UpdateTopControlsState(TopControlsState constraints,
                               TopControlsState current,
                               bool animate) override {}
 
   virtual RendererCapabilities& GetRendererCapabilities();
 
  private:
   RendererCapabilities capabilities_;
   LayerTreeHost* layer_tree_host_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_FAKE_PROXY_H_