cc:: Change plumbing for external_begin_frame_source to the Scheduler.

cc/test/proxy_main_for_test.h

Index: cc/test/proxy_main_for_test.h
diff --git a/cc/test/proxy_main_for_test.h b/cc/test/proxy_main_for_test.h
index 1669cc5a56b831e5399f41f57e19ef7929d090ac..5631701172dd04d3577165b28f7c75d950296058 100644
--- a/cc/test/proxy_main_for_test.h
+++ b/cc/test/proxy_main_for_test.h
@@ -18,15 +18,13 @@ class ProxyMainForTest : public ProxyMain {
   static scoped_ptr<ProxyMain> CreateThreaded(
       TestHooks* test_hooks,
       LayerTreeHost* host,
-      TaskRunnerProvider* task_runner_provider,
-      scoped_ptr<BeginFrameSource> external_begin_frame_source);
+      TaskRunnerProvider* task_runner_provider);
 
   ~ProxyMainForTest() override;
 
   ProxyMainForTest(TestHooks* test_hooks,
                    LayerTreeHost* host,
-                   TaskRunnerProvider* task_runner_provider,
-                   scoped_ptr<BeginFrameSource> external_begin_frame_source);
+                   TaskRunnerProvider* task_runner_provider);
 
   void SetNeedsUpdateLayers() override;
   void DidCompleteSwapBuffers() override;