Bug 1605134 - Fix bustage.

D97403 got overtaken the gtest for AudioInputTrackDisabling. This fixes the
bustage that combination resulted in.

Differential Revision: https://phabricator.services.mozilla.com/D97606

dom/media/gtest/TestAudioTrackGraph.cpp

@@ -529,7 +529,7 @@ TEST(TestAudioTrackGraph, AudioInputTrackDisabling)
     return graph->NotifyWhenDeviceStarted(inputTrack);
   });
 
-  MockCubebStream* stream = WaitFor(cubeb->StreamInitEvent());
+  RefPtr<SmartMockCubebStream> stream = WaitFor(cubeb->StreamInitEvent());
   EXPECT_TRUE(stream->mHasInput);
   Unused << WaitFor(p);