Bug 1321076 - PDMFactory defaults to using VPXDecoder when alpha is present. r=jya

FFmpegDecoderModule and AndroidDecoderModule returns nullptr if alpha is
present, then PDMFactory rolls over to using VPXDecoder.

MozReview-Commit-ID: H2JaolEfJgR

--HG--
extra : rebase_source : a2b4bad848c6350041c2cff805803fb5728342d2

dom/media/platforms/android/AndroidDecoderModule.cpp

@@ -174,6 +174,13 @@ AndroidDecoderModule::SupportsMimeType(const nsACString& aMimeType,
 already_AddRefed<MediaDataDecoder>
 AndroidDecoderModule::CreateVideoDecoder(const CreateDecoderParams& aParams)
 {
+  // Temporary - forces use of VPXDecoder when alpha is present.
+  // Bug 1263836 will handle alpha scenario once implemented. It will shift
+  // the check for alpha to PDMFactory but not itself remove the need for a
+  // check.
+  if (aParams.VideoConfig().HasAlpha()) {
+    return nullptr;
+  }
   MediaFormat::LocalRef format;
 
   const VideoInfo& config = aParams.VideoConfig();

dom/media/platforms/ffmpeg/FFmpegDecoderModule.h

@@ -33,6 +33,13 @@ public:
   already_AddRefed<MediaDataDecoder>
   CreateVideoDecoder(const CreateDecoderParams& aParams) override
   {
+    // Temporary - forces use of VPXDecoder when alpha is present.
+    // Bug 1263836 will handle alpha scenario once implemented. It will shift
+    // the check for alpha to PDMFactory but not itself remove the need for a
+    // check.
+    if (aParams.VideoConfig().HasAlpha()) {
+      return nullptr;
+    }
     RefPtr<MediaDataDecoder> decoder =
       new FFmpegVideoDecoder<V>(mLib,
                                 aParams.mTaskQueue,