Bug 1188220: Allow disabling HW acceleration even when SharedDecoderManager isn't used. r=cpearce

The SharedDecoderManager is being obsoleted.

dom/media/MediaFormatReader.cpp

@@ -504,11 +504,15 @@ void
 MediaFormatReader::DisableHardwareAcceleration()
 {
   MOZ_ASSERT(OnTaskQueue());
-  if (HasVideo() && mSharedDecoderManager) {
-    mSharedDecoderManager->DisableHardwareAcceleration();
-
-    if (!mSharedDecoderManager->Recreate(mInfo.mVideo)) {
-      mVideo.mError = true;
+  if (HasVideo()) {
+    mPlatform->DisableHardwareAcceleration();
+    Flush(TrackInfo::kVideoTrack);
+    mVideo.mDecoder->Shutdown();
+    mVideo.mDecoder = nullptr;
+    if (!EnsureDecodersSetup()) {
+      LOG("Unable to re-create decoder, aborting");
+      NotifyError(TrackInfo::kVideoTrack);
+      return;
     }
     ScheduleUpdate(TrackInfo::kVideoTrack);
   }