Adds BeginFrameControl via DevTools.

cc/surfaces/display_scheduler.h

Index: cc/surfaces/display_scheduler.h
diff --git a/cc/surfaces/display_scheduler.h b/cc/surfaces/display_scheduler.h
index a6a7b467d06d611cbeb3d9fdfb2cd57d72c240f4..1ce03168a5fabb6ac45d15061c1f793865ef5aed 100644
--- a/cc/surfaces/display_scheduler.h
+++ b/cc/surfaces/display_scheduler.h
@@ -13,13 +13,13 @@
 #include "base/single_thread_task_runner.h"
 #include "cc/output/renderer_settings.h"
 #include "cc/scheduler/begin_frame_source.h"
+#include "cc/surfaces/display_begin_frame_source.h"
 #include "cc/surfaces/surface_id.h"
 #include "cc/surfaces/surfaces_export.h"
 
 namespace cc {
 
 class OutputSurface;
-class BeginFrameSource;
 
 class CC_SURFACES_EXPORT DisplaySchedulerClient {
  public:
@@ -28,14 +28,16 @@ class CC_SURFACES_EXPORT DisplaySchedulerClient {
   virtual bool DrawAndSwap() = 0;
 };
 
-class CC_SURFACES_EXPORT DisplayScheduler : public BeginFrameObserverBase {
+class CC_SURFACES_EXPORT DisplayScheduler
+    : public BeginFrameObserverBase,
+      public DisplayBeginFrameSourceClient {
  public:
-  DisplayScheduler(BeginFrameSource* begin_frame_source,
-                   base::SingleThreadTaskRunner* task_runner,
+  DisplayScheduler(base::SingleThreadTaskRunner* task_runner,
                    int max_pending_swaps);
   ~DisplayScheduler() override;
 
   void SetClient(DisplaySchedulerClient* client);
+  void SetBeginFrameSource(DisplayBeginFrameSource* begin_frame_source);
 
   void SetVisible(bool visible);
   void SetRootSurfaceResourcesLocked(bool locked);
@@ -49,10 +51,14 @@ class CC_SURFACES_EXPORT DisplayScheduler : public BeginFrameObserverBase {
 
   void OutputSurfaceLost();
 
-  // BeginFrameObserverBase implementation
+  // BeginFrameObserverBase implementation.
   bool OnBeginFrameDerivedImpl(const BeginFrameArgs& args) override;
   void OnBeginFrameSourcePausedChanged(bool paused) override;
 
+  // DisplayBeginFrameSourceClient implementation.
+  void ObserverStatusChanged() override;
+  void BeginFrameSourceSwapping(BeginFrameSource* new_source) override;
+
  protected:
   base::TimeTicks DesiredBeginFrameDeadlineTime();
   virtual void ScheduleBeginFrameDeadline();
@@ -62,9 +68,10 @@ class CC_SURFACES_EXPORT DisplayScheduler : public BeginFrameObserverBase {
   void StartObservingBeginFrames();
   void StopObservingBeginFrames();
   bool ShouldDraw();
+  bool BeginFrameForcesDamage() const;
 
   DisplaySchedulerClient* client_;
-  BeginFrameSource* begin_frame_source_;
+  DisplayBeginFrameSource* begin_frame_source_;
   base::SingleThreadTaskRunner* task_runner_;
 
   BeginFrameArgs current_begin_frame_args_;