Bug 1258562: MSE] Abort if MediaSource has been shutdown. r=gerald

The assumption was made that this code was never called if MediaSourceDecoder::NextFrameBufferedStatus() had been called before. However, that assumption was incorrect as NextFrameBufferedStatus() is only called if we had determine we had no frame buffered.

MozReview-Commit-ID: 1hsEJuInION

--HG--
extra : rebase_source : f760ef8df01858c24887ba024c6b350332d2e4dc

dom/media/mediasource/MediaSourceDecoder.cpp

@@ -277,6 +277,11 @@ bool
 MediaSourceDecoder::CanPlayThrough()
 {
   MOZ_ASSERT(NS_IsMainThread());
+
+  if (NextFrameBufferedStatus() == MediaDecoderOwner::NEXT_FRAME_UNAVAILABLE) {
+    return false;
+  }
+
   if (IsNaN(mMediaSource->Duration())) {
     // Don't have any data yet.
     return false;