Bug 1329098. Part 2 - remove unnecessary checks. r=kaku

1. mSentFirstFrameLoadedEvent is true in BufferingState.
2. mMinimizePreroll is false in BufferingState for buffering happens after playback starts and we reset mMinimizePreroll once playback starts.

MozReview-Commit-ID: ABE7TvNEetD

--HG--
extra : rebase_source : 53c507ff9cd8ea028c5ff7f8b5b8c049cb8a7ebf
extra : source : e87a70953f6eb8d4a9e31ab06ac73afcc90da923

dom/media/MediaDecoderStateMachine.cpp

@@ -2220,13 +2220,11 @@ BufferingState::DispatchDecodeTasksIfNeeded()
 {
   const bool needToDecodeAudio =
     mMaster->IsAudioDecoding() &&
-    ((!mMaster->mSentFirstFrameLoadedEvent && AudioQueue().GetSize() == 0) ||
-     (!mMaster->mMinimizePreroll && !mMaster->HaveEnoughDecodedAudio()));
+   !mMaster->HaveEnoughDecodedAudio();
 
   const bool needToDecodeVideo =
     mMaster->IsVideoDecoding() &&
-    ((!mMaster->mSentFirstFrameLoadedEvent && VideoQueue().GetSize() == 0) ||
-     (!mMaster->mMinimizePreroll && !mMaster->HaveEnoughDecodedVideo()));
+    !mMaster->HaveEnoughDecodedVideo();
 
   if (needToDecodeAudio) {
     mMaster->EnsureAudioDecodeTaskQueued();