Bug 1694634 - part4 : correct the comment for LoopingDecodingState. r=bryce

At the time I worked on this state, it was only used for audio. There were some problems blocking the implementation for video, but the comment wasn't updated.

So we should correct the comment to make it reflect the real situation.

Differential Revision: https://phabricator.services.mozilla.com/D110881

dom/media/MediaDecoderStateMachine.cpp

@@ -769,16 +769,17 @@ class MediaDecoderStateMachine::DecodingState
 };
 
 /**
- * Purpose: decode audio/video data for playback when media is in seamless
+ * Purpose: decode audio data for playback when media is in seamless
  * looping, we will adjust media time to make samples time monotonically
- * increasing.
+ * increasing. Note, it's currently used for audio-only, but we should make it
+ * work on video as well in bug 1262276.
  *
  * Transition to:
  *   DORMANT if playback is paused for a while.
  *   SEEKING if any seek request.
  *   SHUTDOWN if any decode error.
  *   BUFFERING if playback can't continue due to lack of decoded data.
- *   COMPLETED when having decoded all audio/video data.
+ *   COMPLETED when having decoded all audio data.
  *   DECODING when media stop seamless looping
  */
 class MediaDecoderStateMachine::LoopingDecodingState