Let CreateVideoDecoder take a cricket::VideoCodec.

webrtc/sdk/objc/Framework/Classes/VideoToolbox/objc_video_decoder_factory.mm

Index: webrtc/sdk/objc/Framework/Classes/VideoToolbox/objc_video_decoder_factory.mm
diff --git a/webrtc/sdk/objc/Framework/Classes/VideoToolbox/objc_video_decoder_factory.mm b/webrtc/sdk/objc/Framework/Classes/VideoToolbox/objc_video_decoder_factory.mm
index 26e73d97001edf2d9df86930d8417e7872c0ce91..499a5e028a99b125b1774e72d1113a85c1031cb2 100644
--- a/webrtc/sdk/objc/Framework/Classes/VideoToolbox/objc_video_decoder_factory.mm
+++ b/webrtc/sdk/objc/Framework/Classes/VideoToolbox/objc_video_decoder_factory.mm
@@ -103,10 +103,8 @@ id<RTCVideoDecoderFactory> ObjCVideoDecoderFactory::wrapped_decoder_factory() co
   return decoder_factory_;
 }
 
-VideoDecoder *ObjCVideoDecoderFactory::CreateVideoDecoder(VideoCodecType type) {
-  const char *codec_name = CodecTypeToPayloadName(type);
-
-  NSString *codecName = [NSString stringWithUTF8String:codec_name];
+VideoDecoder *ObjCVideoDecoderFactory::CreateVideoDecoder(const cricket::VideoCodec &codec) {
+  NSString *codecName = [NSString stringWithUTF8String:codec.name.c_str()];

[magjed_webrtc, 2017/08/24 08:59:39]

I think we could simplify this whole function now by just doing:
id<RTCVideoDecoder> decoder = [decoder_factory_ createDecoder:[RTCVideoCodecInfo
initWithNativeVideoCodec:codec]];
return decoder ? new ObjCVideoDecoder(decoder) : nullptr;

[kthelgason, 2017/08/24 10:49:47]

Sure, we can do that, but that just moves the responsibility of making sure that
the codec being asked for is supported by the decoder.
I'd prefer to keep it like this for now, and if we decide to change it I think
it's a separate change.

[magjed_webrtc, 2017/08/25 15:55:01]

I think we should fix the C++ code in core WebRTC so that we don't try to create
invalid decoders in the first place, but let's fix it in a separate change as
you suggest.

   for (RTCVideoCodecInfo *codecInfo in decoder_factory_.supportedCodecs) {
     if ([codecName isEqualToString:codecInfo.name]) {
       id<RTCVideoDecoder> decoder = [decoder_factory_ createDecoder:codecInfo];