Refactoring the way begin frame sources inside scheduler work.

cc/scheduler/scheduler.h

Index: cc/scheduler/scheduler.h
diff --git a/cc/scheduler/scheduler.h b/cc/scheduler/scheduler.h
index 1e59192a0f4f06003f1a75e5f5c9fc8b101bdd12..ff0c042c7affea062c80f09016f99fed8ba3b36a 100644
--- a/cc/scheduler/scheduler.h
+++ b/cc/scheduler/scheduler.h
@@ -15,6 +15,7 @@
 #include "cc/base/cc_export.h"
 #include "cc/output/begin_frame_args.h"
 #include "cc/scheduler/draw_swap_readback_result.h"
+#include "cc/scheduler/frame_source.h"
 #include "cc/scheduler/scheduler_settings.h"
 #include "cc/scheduler/scheduler_state_machine.h"
 #include "cc/scheduler/time_source.h"
@@ -23,11 +24,9 @@
 namespace cc {
 
 class Thread;
-class SyntheticBeginFrameSource;
 
 class SchedulerClient {
  public:
-  virtual void SetNeedsBeginFrame(bool enable) = 0;
   virtual void WillBeginImplFrame(const BeginFrameArgs& args) = 0;
   virtual void ScheduledActionSendBeginMainFrame() = 0;
   virtual DrawSwapReadbackResult ScheduledActionDrawAndSwapIfPossible() = 0;
@@ -49,15 +48,19 @@ class SchedulerClient {
   virtual ~SchedulerClient() {}
 };
 
-class CC_EXPORT Scheduler {
+class CC_EXPORT Scheduler : public FrameSink {
  public:
   static scoped_ptr<Scheduler> Create(
       SchedulerClient* client,
       const SchedulerSettings& scheduler_settings,
       int layer_tree_host_id,
+      FrameSource* external_frame_source,
       const scoped_refptr<base::SingleThreadTaskRunner>& impl_task_runner) {
-    return make_scoped_ptr(new Scheduler(
-        client, scheduler_settings, layer_tree_host_id, impl_task_runner));
+    return make_scoped_ptr(new Scheduler(client,
+                                         scheduler_settings,
+                                         layer_tree_host_id,
+                                         external_frame_source,
+                                         impl_task_runner));
   }
 
   virtual ~Scheduler();
@@ -127,10 +130,9 @@ class CC_EXPORT Scheduler {
     return estimated_parent_draw_time_;
   }
 
-  void BeginFrame(const BeginFrameArgs& args);
+  virtual void BeginFrame(const BeginFrameArgs& args) OVERRIDE;
   void PostBeginRetroFrame();
   void BeginRetroFrame();
-  void BeginUnthrottledFrame();
 
   void BeginImplFrame(const BeginFrameArgs& args);
   void OnBeginImplFrameDeadline();
@@ -153,6 +155,7 @@ class CC_EXPORT Scheduler {
       SchedulerClient* client,
       const SchedulerSettings& scheduler_settings,
       int layer_tree_host_id,
+      FrameSource* external_frame_source,
       const scoped_refptr<base::SingleThreadTaskRunner>& impl_task_runner);
 
   base::TimeTicks AdjustedBeginImplFrameDeadline(
@@ -189,8 +192,7 @@ class CC_EXPORT Scheduler {
   std::deque<BeginFrameArgs> begin_retro_frame_args_;
   BeginFrameArgs begin_impl_frame_args_;
 
-  void SetupSyntheticBeginFrames();
-  scoped_ptr<SyntheticBeginFrameSource> synthetic_begin_frame_source_;
+  scoped_ptr<DualFrameSource> frame_source_;
 
   base::Closure begin_retro_frame_closure_;
   base::Closure begin_unthrottled_frame_closure_;