Make SingleThreadProxy a SchedulerClient

ui/compositor/test/draw_waiter_for_test.h

Index: ui/compositor/test/draw_waiter_for_test.h
diff --git a/ui/compositor/test/draw_waiter_for_test.h b/ui/compositor/test/draw_waiter_for_test.h
index 051c58fe3940f170fecaf437c5af91d165b2972d..e1d63ff00132814156fbdf9a560b599a94097eb1 100644
--- a/ui/compositor/test/draw_waiter_for_test.h
+++ b/ui/compositor/test/draw_waiter_for_test.h
@@ -20,13 +20,22 @@ class DrawWaiterForTest : public CompositorObserver {
   // Waits for a draw to be issued by the compositor. If the test times out
   // here, there may be a logic error in the compositor code causing it
   // not to draw.
-  static void Wait(Compositor* compositor);
+  static void WaitForCompositingStarted(Compositor* compositor);
+
+  // Waits for a swap to be completed from the compositor.
+  static void WaitForCompositingEnded(Compositor* compositor);
 
   // Waits for a commit instead of a draw.
   static void WaitForCommit(Compositor* compositor);
 
  private:
-  DrawWaiterForTest();
+  enum WaitEvent {
+    WAIT_FOR_COMMIT,
+    WAIT_FOR_COMPOSITING_STARTED,
+    WAIT_FOR_COMPOSITING_ENDED,
+  };
+
+  DrawWaiterForTest(WaitEvent wait_event);
   virtual ~DrawWaiterForTest();
 
   void WaitImpl(Compositor* compositor);
@@ -41,7 +50,7 @@ class DrawWaiterForTest : public CompositorObserver {
 
   scoped_ptr<base::RunLoop> wait_run_loop_;
 
-  bool wait_for_commit_;
+  WaitEvent wait_event_;
 
   DISALLOW_COPY_AND_ASSIGN(DrawWaiterForTest);
 };