Bug 1371200. P4 - constify some members. r=cpearce

MozReview-Commit-ID: B7rrXrTn7RD

--HG--
extra : rebase_source : cdca8a7a313d0c066aac58083e4b63e1be83603d
extra : source : 4d818f16afa3763b2515bdb9834880f11aa13989

dom/media/MediaDecoder.h

@@ -690,13 +690,13 @@ protected:
 
   // Be assigned from media element during the initialization and pass to
   // AudioStream Class.
-  dom::AudioChannel mAudioChannel;
+  const dom::AudioChannel mAudioChannel;
 
   // True if the decoder has been directed to minimize its preroll before
   // playback starts. After the first time playback starts, we don't attempt
   // to minimize preroll, as we assume the user is likely to keep playing,
   // or play the media again.
-  bool mMinimizePreroll;
+  const bool mMinimizePreroll;
 
   // True if we've already fired metadataloaded.
   bool mFiredMetadataLoaded;