Replace WaitableEvents and ConditionalVariables in VideoRendererBase tests with MessageLoop.

media/base/mock_callback.h

Index: media/base/mock_callback.h
diff --git a/media/base/mock_callback.h b/media/base/mock_callback.h
index 00d8276067cb441763d23544f8eff69ba0d43159..499d95d12281e84c7b6d6cad4ea5ce6e992bc01a 100644
--- a/media/base/mock_callback.h
+++ b/media/base/mock_callback.h
@@ -29,7 +29,10 @@ class MockClosure : public base::RefCountedThreadSafe<MockClosure> {
 
 // Return a callback that expects to be run once.
 base::Closure NewExpectedClosure();
-base::Callback<void(PipelineStatus)> NewExpectedStatusCB(PipelineStatus status);
+PipelineStatusCB NewExpectedStatusCB(PipelineStatus status);
+
+// Returns a PipelineStatusCB that quits the current message loop after running.
+PipelineStatusCB NewExpectedStatusAndQuitCB(PipelineStatus status);
 
 }  // namespace media