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

- Bug 1148102: P5. Add Opus/VPX/Vorbis MediaDataDecoder. r=jya (b07fea1ea)
- Bug 1148102: P6. Add WebMDemuxer object. r=jya (225cee37f)
- reformat comment (9d12af823)
- reformat comment (80765706d)
- Bug 1148102: P7. Hookup WebMDemuxer. r=jya (78f973b17)
-  Bug 1185782 - Remove media.windows-media-foundation.enabled pref. r=jya (2fb2c5e4a)
- Bug 1163486 - Remove MP4Reader. r=jya (0376d6d60)
and some custom changes for our tree:
- change MediaReadAt to SilentReadAt in new file dom/media/webm/WebMDemuxer.cpp
- add missing export of "vpx_codec_err_to_string" in layout/media/symbols.def.in

dom/media/platforms/PlatformDecoderModule.cpp

@@ -32,8 +32,13 @@
 #include "MediaInfo.h"
 #include "H264Converter.h"
 
+#include "OpusDecoder.h"
+#include "VorbisDecoder.h"
+#include "VPXDecoder.h"
+
 namespace mozilla {
 
+extern already_AddRefed<PlatformDecoderModule> CreateAgnosticDecoderModule();
 extern already_AddRefed<PlatformDecoderModule> CreateBlankDecoderModule();
 
 bool PlatformDecoderModule::sUseBlankDecoder = false;
@@ -99,7 +104,7 @@ PlatformDecoderModule::Create()
   if (m && NS_SUCCEEDED(m->Startup())) {
     return m.forget();
   }
-  return nullptr;
+  return CreateAgnosticDecoderModule();
 }
 
 /* static */
@@ -159,10 +164,22 @@ PlatformDecoderModule::CreateDecoder(const TrackInfo& aConfig,
 {
   nsRefPtr<MediaDataDecoder> m;
 
+  bool hasPlatformDecoder = SupportsMimeType(aConfig.mMimeType);
+
   if (aConfig.GetAsAudioInfo()) {
-    m = CreateAudioDecoder(*aConfig.GetAsAudioInfo(),
-                           aTaskQueue,
-                           aCallback);
+    if (!hasPlatformDecoder && VorbisDataDecoder::IsVorbis(aConfig.mMimeType)) {
+      m = new VorbisDataDecoder(*aConfig.GetAsAudioInfo(),
+                                aTaskQueue,
+                                aCallback);
+    } else if (!hasPlatformDecoder && OpusDataDecoder::IsOpus(aConfig.mMimeType)) {
+      m = new OpusDataDecoder(*aConfig.GetAsAudioInfo(),
+                              aTaskQueue,
+                              aCallback);
+    } else {
+      m = CreateAudioDecoder(*aConfig.GetAsAudioInfo(),
+                             aTaskQueue,
+                             aCallback);
+    }
     return m.forget();
   }
 
@@ -185,6 +202,11 @@ PlatformDecoderModule::CreateDecoder(const TrackInfo& aConfig,
       // problem, for example WMF DLLs were missing.
       m = h.forget();
     }
+  } else if (!hasPlatformDecoder && VPXDecoder::IsVPX(aConfig.mMimeType)) {
+    m = new VPXDecoder(*aConfig.GetAsVideoInfo(),
+                       aImageContainer,
+                       aTaskQueue,
+                       aCallback);
   } else {
     m = CreateVideoDecoder(*aConfig.GetAsVideoInfo(),
                            aLayersBackend,
@@ -203,4 +225,14 @@ PlatformDecoderModule::SupportsMimeType(const nsACString& aMimeType)
          aMimeType.EqualsLiteral("video/avc");
 }
 
+/* static */
+bool
+PlatformDecoderModule::AgnosticMimeType(const nsACString& aMimeType)
+{
+  return VPXDecoder::IsVPX(aMimeType) ||
+    OpusDataDecoder::IsOpus(aMimeType) ||
+    VorbisDataDecoder::IsVorbis(aMimeType);
+}
+
+
 } // namespace mozilla