Split out dscp option from VideoOptions to new struct MediaChannelOptions.

webrtc/media/base/rtpdataengine.cc

Index: webrtc/media/base/rtpdataengine.cc
diff --git a/webrtc/media/base/rtpdataengine.cc b/webrtc/media/base/rtpdataengine.cc
index df104f69a29b5ed51b0892853768f2c27da310a3..4ceeeabaede1a62bf5ba3798cc920e56a6d13365 100644
--- a/webrtc/media/base/rtpdataengine.cc
+++ b/webrtc/media/base/rtpdataengine.cc
@@ -78,11 +78,13 @@ bool FindCodecByName(const std::vector<DataCodec>& codecs,
   return false;
 }
 
-RtpDataMediaChannel::RtpDataMediaChannel(rtc::Timing* timing) {
+RtpDataMediaChannel::RtpDataMediaChannel(rtc::Timing* timing)
+    : DataMediaChannel(MediaChannelOptions()) {
   Construct(timing);
 }
 
-RtpDataMediaChannel::RtpDataMediaChannel() {
+RtpDataMediaChannel::RtpDataMediaChannel()
+    : DataMediaChannel(MediaChannelOptions()) {
   Construct(NULL);
 }