Bug 1303902: [FLAC] Actually check that we found the first frame. r=kamidphish

MozReview-Commit-ID: 3VRf49DqB00

--HG--
extra : rebase_source : b357a310bf6242b07a1c72ce05ae285fe18cd2a1

dom/media/flac/FlacDemuxer.cpp

@@ -676,7 +676,7 @@ FlacTrackDemuxer::Init()
     // Ensure that the next frame returned will be the first.
     mSource.Seek(SEEK_SET, mParser->FirstFrame().Offset());
     mParser->EndFrameSession();
-  } else if (!mParser->Info().IsValid()) {
+  } else if (!mParser->Info().IsValid() || !mParser->FirstFrame().IsValid()) {
     // We must find at least a frame to determine the metadata.
     // We can't play this stream.
     return false;