Revert of Remove CompositorObserver::OnCompositingEnded()

ui/compositor/test/draw_waiter_for_test.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/compositor/test/draw_waiter_for_test.h"
 
 #include "ui/compositor/compositor.h"
 
 namespace ui {
 
 // static
 void DrawWaiterForTest::WaitForCompositingStarted(Compositor* compositor) {
   DrawWaiterForTest waiter(WAIT_FOR_COMPOSITING_STARTED);
   waiter.WaitImpl(compositor);
 }
 
+void DrawWaiterForTest::WaitForCompositingEnded(Compositor* compositor) {
+  DrawWaiterForTest waiter(WAIT_FOR_COMPOSITING_ENDED);
+  waiter.WaitImpl(compositor);
+}
+
 // static
 void DrawWaiterForTest::WaitForCommit(Compositor* compositor) {
   DrawWaiterForTest waiter(WAIT_FOR_COMMIT);
   waiter.WaitImpl(compositor);
 }
 
 DrawWaiterForTest::DrawWaiterForTest(WaitEvent wait_event)
     : wait_event_(wait_event) {
 }
 
@@ skipping 10 matching lines @@
   if (wait_event_ == WAIT_FOR_COMMIT)
     wait_run_loop_->Quit();
 }
 
 void DrawWaiterForTest::OnCompositingStarted(Compositor* compositor,
                                              base::TimeTicks start_time) {
   if (wait_event_ == WAIT_FOR_COMPOSITING_STARTED)
     wait_run_loop_->Quit();
 }
 
+void DrawWaiterForTest::OnCompositingEnded(Compositor* compositor) {
+  if (wait_event_ == WAIT_FOR_COMPOSITING_ENDED)
+    wait_run_loop_->Quit();
+}
+
 void DrawWaiterForTest::OnCompositingLockStateChanged(Compositor* compositor) {}
 
 void DrawWaiterForTest::OnCompositingShuttingDown(Compositor* compositor) {}
 
 }  // namespace ui