AppRTCMobile iOS: Use video encoder factory to manage codec preference.

List codecs from factory in settings, select by changing order in factory.

Bug: webrtc:7925
Change-Id: If3c45e56713104c88705c67560325d002e6d6700
Reviewed-on: https://webrtc-review.googlesource.com/3720
Commit-Queue: Anders Carlsson <andersc@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20312}

sdk/objc/Framework/Classes/PeerConnection/RTCVideoCodec.mm

@@ -89,6 +89,18 @@
   return codec;
 }
 
+#pragma mark - NSCoding
+
+- (instancetype)initWithCoder:(NSCoder *)decoder {
+  return [self initWithName:[decoder decodeObjectForKey:@"name"]
+                 parameters:[decoder decodeObjectForKey:@"parameters"]];
+}
+
+- (void)encodeWithCoder:(NSCoder *)encoder {
+  [encoder encodeObject:_name forKey:@"name"];
+  [encoder encodeObject:_parameters forKey:@"parameters"];
+}
+
 @end
 
 @implementation RTCVideoEncoderQpThresholds