import changes from `dev' branch of rmottola/Arctic-Fox:

- Bug 1175768 - Remove bogus check. r=jya (6d1b387f4)
- Bug 1175768 - Make the logic in MDSM::NotifyDataArrived apply to mObservedDuration. r=jya (90dcae693)
- Bug 1175768 - Dispatch UpdateEstimatedMediaDuration. r=jya (f003b4646)
- Bug 1175768 - Dispatch NotifyDataArrived and remove the aBuffer argument. r=jya (e6eaf8eb1)
- Bug 1175768 - Misc changes to Intervals/TimeUnit. r=jya (786da5ba2)
- Bug 1174220 - Part 2: Use MediaByteBuffer instead of MediaLargeByteBuffer. r=jya (59fe3c482)
- Bug 1175768 - Use mirroring for buffered ranges. r=jya (5100aba5e)
- Bug 1175768 - Throttle NotifyDataArrived. r=jya (4bb13775b)
- Bug 1178680 - Remove MediaDecoder::Observe as we have MediaShutdownManager. r=cpearce. (ba9b728ea)
- Bug 1178437 - Do the dormant-enabled tracking on the main thread. r=jww,r=jya (b0287df66)

dom/media/fmp4/MP4Decoder.cpp

@@ -32,6 +32,19 @@
 
 namespace mozilla {
 
+#if defined(MOZ_GONK_MEDIACODEC) || defined(XP_WIN) || defined(MOZ_APPLEMEDIA) || defined(MOZ_FFMPEG)
+#define MP4_READER_DORMANT_HEURISTIC
+#else
+#undef MP4_READER_DORMANT_HEURISTIC
+#endif
+
+MP4Decoder::MP4Decoder()
+{
+#if defined(MP4_READER_DORMANT_HEURISTIC)
+  mDormantSupported = Preferences::GetBool("media.decoder.heuristic.dormant.enabled", false);
+#endif
+}
+
 MediaDecoderStateMachine* MP4Decoder::CreateStateMachine()
 {
   bool useFormatDecoder =