Hook up ui::Compositor to Display's BeginFrameSource

cc/test/fake_output_surface_client.h

Index: cc/test/fake_output_surface_client.h
diff --git a/cc/test/fake_output_surface_client.h b/cc/test/fake_output_surface_client.h
index c9a5efa062bf123b549e557c362894e36eda303e..bb0371582b2cd5a008958cf93acf7609e4c050d5 100644
--- a/cc/test/fake_output_surface_client.h
+++ b/cc/test/fake_output_surface_client.h
@@ -21,6 +21,7 @@ class FakeOutputSurfaceClient : public OutputSurfaceClient {
 
   void CommitVSyncParameters(base::TimeTicks timebase,
                              base::TimeDelta interval) override {}
+  void SetBeginFrameSource(BeginFrameSource* source) override {}
   void SetNeedsRedrawRect(const gfx::Rect& damage_rect) override {}
   void DidSwapBuffers() override;
   void DidSwapBuffersComplete() override {}