Implement SpeechRecognizerImplAndroid

content/public/browser/speech_recognition_event_listener.h

Index: content/public/browser/speech_recognition_event_listener.h
diff --git a/content/public/browser/speech_recognition_event_listener.h b/content/public/browser/speech_recognition_event_listener.h
index 986491299bb02680a8620df8bbd8ebc224bbc17d..8c16f9099cf56eea5563507eeff08d9a69b2d2be 100644
--- a/content/public/browser/speech_recognition_event_listener.h
+++ b/content/public/browser/speech_recognition_event_listener.h
@@ -53,6 +53,8 @@ class CONTENT_EXPORT SpeechRecognitionEventListener {
   // Informs of a change in the captured audio level, useful if displaying
   // a microphone volume indicator while recording.
   // The value of |volume| and |noise_volume| is in the [0.0, 1.0] range.
+  // TODO(janx): Is this necessary? It looks like only x-webkit-speech bubble
+  // uses it (see crbug.com/247351).
   virtual void OnAudioLevelsChange(int session_id,
                                    float volume, float noise_volume) = 0;