Bug 1390748 - Create DecoderTraits::IsSupportedType(const MediaContainerType&). r=jwwang

Most ChannelMediaDecoder::CloneImpl() functions just check to see whether
their "is enabled" pref is still true, and then clone their true type.

If we had a function to check whether the decoder for an arbitrary type
was still enabled, we'd not need the "is enabled" checks in the CloneImpl()
implementations. We'd then have removed the last custom behaviour in the
ChannelMediaDecoder subclasses.


MozReview-Commit-ID: D7kW6kb6ztW

--HG--
extra : rebase_source : f463785d2975adceffd62037315d169736effbc0

dom/media/DecoderTraits.cpp

@@ -323,6 +323,30 @@ DecoderTraits::CreateReader(const MediaContainerType& aType,
   return decoderReader;
 }
 
+/* static */
+bool
+DecoderTraits::IsSupportedType(const MediaContainerType& aType)
+{
+  typedef bool (*IsSupportedFunction)(const MediaContainerType& aType);
+  static const IsSupportedFunction funcs[] = {
+    &ADTSDecoder::IsSupportedType,
+    &FlacDecoder::IsSupportedType,
+    &MP3Decoder::IsSupportedType,
+#ifdef MOZ_FMP4
+    &MP4Decoder::IsSupportedTypeWithoutDiagnostics,
+#endif
+    &OggDecoder::IsSupportedType,
+    &WaveDecoder::IsSupportedType,
+    &WebMDecoder::IsSupportedType,
+  };
+  for (IsSupportedFunction func : funcs) {
+    if (func(aType)) {
+      return true;
+    }
+  }
+  return false;
+}
+
 /* static */
 bool DecoderTraits::IsSupportedInVideoDocument(const nsACString& aType)
 {

dom/media/DecoderTraits.h

@@ -65,6 +65,8 @@ public:
 
   // Returns true if aType is MIME type of hls.
   static bool IsHttpLiveStreamingType(const MediaContainerType& aType);
+
+  static bool IsSupportedType(const MediaContainerType& aType);
 };
 
 } // namespace mozilla

dom/media/fmp4/MP4Decoder.cpp

@@ -55,6 +55,14 @@ IsWhitelistedH264Codec(const nsAString& aCodec)
           profile == H264_PROFILE_HIGH);
 }
 
+/* static */
+bool
+MP4Decoder::IsSupportedTypeWithoutDiagnostics(
+  const MediaContainerType& aContainerType)
+{
+  return IsSupportedType(aContainerType, nullptr);
+}
+
 /* static */
 bool
 MP4Decoder::IsSupportedType(const MediaContainerType& aType,

dom/media/fmp4/MP4Decoder.h

@@ -26,6 +26,9 @@ public:
   static bool IsSupportedType(const MediaContainerType& aContainerType,
                               DecoderDoctorDiagnostics* aDiagnostics);
 
+  static bool IsSupportedTypeWithoutDiagnostics(
+    const MediaContainerType& aContainerType);
+
   // Return true if aMimeType is a one of the strings used by our demuxers to
   // identify H264. Does not parse general content type strings, i.e. white
   // space matters.