Bug 1331554. Part 1 - print logs only when decoder.mIsBlankDecode is going to change. r=jya

MozReview-Commit-ID: 9vExcUapFOb

--HG--
extra : rebase_source : 9d10701d7d7dd973272f24c3ef02d2825c7448b8
extra : intermediate-source : ec68e23b75cc3e4ffcc1304a8f74b8b7348bd8f6
extra : source : 2b4b139920482a0d5dcfbbfa461cc093d32a3ae1

dom/media/MediaFormatReader.cpp

@@ -2726,15 +2726,15 @@ void
 MediaFormatReader::SetBlankDecode(TrackType aTrack, bool aIsBlankDecode)
 {
   MOZ_ASSERT(OnTaskQueue());
+
   auto& decoder = GetDecoderData(aTrack);
-
-  LOG("%s, decoder.mIsBlankDecode = %d => aIsBlankDecode = %d",
-      TrackTypeToStr(aTrack), decoder.mIsBlankDecode, aIsBlankDecode);
-
   if (decoder.mIsBlankDecode == aIsBlankDecode) {
     return;
   }
 
+  LOG("%s, decoder.mIsBlankDecode = %d => aIsBlankDecode = %d",
+      TrackTypeToStr(aTrack), decoder.mIsBlankDecode, aIsBlankDecode);
+
   decoder.mIsBlankDecode = aIsBlankDecode;
   decoder.Flush();
   decoder.ShutdownDecoder();