Improve input handling for WaveAudioHandler.

media/audio/sounds/sounds_manager.cc

Index: media/audio/sounds/sounds_manager.cc
diff --git a/media/audio/sounds/sounds_manager.cc b/media/audio/sounds/sounds_manager.cc
index 17f0dd874368f89c23c2aab57749e9c771b8282f..35f467b4d78dd8eeea5359620cc07c0384c5335d 100644
--- a/media/audio/sounds/sounds_manager.cc
+++ b/media/audio/sounds/sounds_manager.cc
@@ -89,8 +89,10 @@ base::TimeDelta SoundsManagerImpl::GetDuration(SoundKey key) {
       return base::TimeDelta();
   if (!handler->IsInitialized())
     return base::TimeDelta();
-  const WavAudioHandler& wav_audio = handler->wav_audio_handler();
-  return wav_audio.GetDuration();
+
+  const WavAudioHandler* wav_audio = handler->wav_audio_handler();
+  DCHECK(wav_audio);
+  return wav_audio->GetDuration();
 }
 
 linked_ptr<AudioStreamHandler> SoundsManagerImpl::GetHandler(SoundKey key) {