Add support for AV1 in MP4

dom/media/fmp4/MP4Decoder.cpp

@@ -147,6 +147,14 @@ MP4Decoder::CanHandleMediaType(const MediaContentType& aType,
             NS_LITERAL_CSTRING("audio/flac"), aType));
         continue;
       }
+#ifdef MOZ_AV1
+    if (IsAV1CodecString(codec)) {
+      trackInfos.AppendElement(
+          CreateTrackInfoWithMIMETypeAndContentTypeExtraParameters(
+          NS_LITERAL_CSTRING("video/av1"), aType));
+      continue;
+    }
+#endif
       // Note: Only accept H.264 in a video content type, not in an audio
       // content type.
       if (IsWhitelistedH264Codec(codec) && isMP4Video) {