Improve input handling for WaveAudioHandler.

media/audio/sounds/audio_stream_handler.h

Index: media/audio/sounds/audio_stream_handler.h
diff --git a/media/audio/sounds/audio_stream_handler.h b/media/audio/sounds/audio_stream_handler.h
index f814aaef5993b793052fd54bf80105f8c634d57e..2dd77d68e49518af683ce7a32d01ef12cb8fcbb2 100644
--- a/media/audio/sounds/audio_stream_handler.h
+++ b/media/audio/sounds/audio_stream_handler.h
@@ -53,7 +53,8 @@ class MEDIA_EXPORT AudioStreamHandler : public base::NonThreadSafe {
   // Stops current playback.
   void Stop();
 
-  const WavAudioHandler& wav_audio_handler() const { return wav_audio_; }
+  // If AudioStreamHandler is not initialized, this will return nullptr.
+  const WavAudioHandler* wav_audio_handler() const { return wav_audio_.get(); }
 
  private:
   friend class AudioStreamHandlerTest;
@@ -65,7 +66,7 @@ class MEDIA_EXPORT AudioStreamHandler : public base::NonThreadSafe {
   static void SetAudioSourceForTesting(
       AudioOutputStream::AudioSourceCallback* source);
 
-  WavAudioHandler wav_audio_;
+  scoped_ptr<WavAudioHandler> wav_audio_;
   scoped_ptr<AudioStreamContainer> stream_;
 
   bool initialized_;