Hook up ui::Compositor to Display's BeginFrameSource

cc/test/fake_layer_tree_host_impl_client.h

Index: cc/test/fake_layer_tree_host_impl_client.h
diff --git a/cc/test/fake_layer_tree_host_impl_client.h b/cc/test/fake_layer_tree_host_impl_client.h
index cf2525baafb6859600ffffb3e591d048b83a962f..fc21844e7b0b15dc5419ffe19060300bf7b05ea8 100644
--- a/cc/test/fake_layer_tree_host_impl_client.h
+++ b/cc/test/fake_layer_tree_host_impl_client.h
@@ -18,6 +18,7 @@ class FakeLayerTreeHostImplClient : public LayerTreeHostImplClient {
   void DidLoseOutputSurfaceOnImplThread() override {}
   void CommitVSyncParameters(base::TimeTicks timebase,
                              base::TimeDelta interval) override {}
+  void SetBeginFrameSource(BeginFrameSource* source) override {}
   void SetEstimatedParentDrawTime(base::TimeDelta draw_time) override {}
   void DidSwapBuffersOnImplThread() override {}
   void DidSwapBuffersCompleteOnImplThread() override {}