Disable MediaStreamAudioTest.CallbackOnTrackInitialization on Mac.

Disabling the test, because it has been consistently failing
for the last 3 builds on Mac10.9 Tests (dbg).  OTOH, note that
FindIt says that it cannot find the culprit CL and thinks that
the test is just flaky.  In either case, disabling the test seems like
the right thing to do.

BUG=709231
TBR=hta@chromium.org

Review-Url: https://codereview.chromium.org/2799663006
Cr-Commit-Position: refs/heads/master@{#462701}

content/renderer/media/media_stream_audio_unittest.cc

@@ -460,8 +460,15 @@ TEST_F(MediaStreamAudioTest, EnableAndDisableTracks) {
   track()->RemoveSink(&sink);
 }
 
+// https://crbug.com/709231 tracks test failures on Mac10.9 Tests (dbg).
+#if defined(OS_MACOSX)
+#define MAYBE_CallbackOnTrackInitialization \
+  DISABLED_CallbackOnTrackInitialization
+#else
+#define MAYBE_CallbackOnTrackInitialization CallbackOnTrackInitialization
+#endif
 // Tests that a callback is fired when initialization completes on a track.
-TEST_F(MediaStreamAudioTest, CallbackOnTrackInitialization) {
+TEST_F(MediaStreamAudioTest, MAYBE_CallbackOnTrackInitialization) {
   // Create a source, connect it to track, and connect the track to a
   // sink.
   blink_audio_source_.setExtraData(new FakeMediaStreamAudioSource());