[Chromecast] Add a return value after NOTREACHED in tests.

chromecast/media/audio/cast_audio_output_stream_unittest.cc

Index: chromecast/media/audio/cast_audio_output_stream_unittest.cc
diff --git a/chromecast/media/audio/cast_audio_output_stream_unittest.cc b/chromecast/media/audio/cast_audio_output_stream_unittest.cc
index a1e491aa48b1d98e5852111e8da6266e96798620..8d885f957c98cf9adc13feb332def5b7097624c0 100644
--- a/chromecast/media/audio/cast_audio_output_stream_unittest.cc
+++ b/chromecast/media/audio/cast_audio_output_stream_unittest.cc
@@ -80,8 +80,12 @@ class FakeAudioPipelineDevice : public AudioPipelineDevice {
         return kFramePending;
       case PIPELINE_STATUS_ERROR:
         return kFrameFailed;
+      default:
+        NOTREACHED();
     }
-    NOTREACHED();
+
+    // This will never be reached but is necessary for compiler warnings.
+    return kFrameFailed;
   }
   RenderingDelay GetRenderingDelay() const override { return RenderingDelay(); }
   bool GetStatistics(Statistics* stats) const override { return false; }