Adds BeginFrameControl via DevTools.

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 76f8f38765127232647b1fd02031924eb7782e3b..4d60d290554d4383363ecd54083a12468eb3d6f4 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -39,6 +39,7 @@ class SingleThreadTaskRunner;
 namespace cc {
 class AnimationHost;
 class AnimationTimeline;
+class BeginFrameSource;
 class ContextProvider;
 class Layer;
 class LayerTreeDebugState;
@@ -155,6 +156,10 @@ class COMPOSITOR_EXPORT ContextFactory {
                                          base::TimeTicks timebase,
                                          base::TimeDelta interval) = 0;
 
+  virtual void SwapBeginFrameSource(
+      ui::Compositor* compositor,
+      std::unique_ptr<cc::BeginFrameSource>* begin_frame_source) = 0;
+
   virtual void SetOutputIsSecure(Compositor* compositor, bool secure) = 0;
 
   virtual void AddObserver(ContextFactoryObserver* observer) = 0;
@@ -285,6 +290,10 @@ class COMPOSITOR_EXPORT Compositor
   void SetDisplayVSyncParameters(base::TimeTicks timebase,
                                  base::TimeDelta interval);
 
+  // See Display::SwapBeginFrameSource.
+  void SwapBeginFrameSource(
+      std::unique_ptr<cc::BeginFrameSource>* begin_frame_source);
+
   // Sets the widget for the compositor to render into.
   void SetAcceleratedWidget(gfx::AcceleratedWidget widget);
   // Releases the widget previously set through SetAcceleratedWidget().