Add RtcpMuxPolicy to PeerConnection.

public/platform/WebRTCConfiguration.h

Index: public/platform/WebRTCConfiguration.h
diff --git a/public/platform/WebRTCConfiguration.h b/public/platform/WebRTCConfiguration.h
index e8140522bf23417f0e0c919a4cf11ca0d1d6ff59..9398a49ac9e3c2964e563083400dd4aaf4b24bb2 100644
--- a/public/platform/WebRTCConfiguration.h
+++ b/public/platform/WebRTCConfiguration.h
@@ -84,6 +84,11 @@ enum WebRTCBundlePolicy {
     WebRTCBundlePolicyMaxBundle
 };
 
+enum WebRTCRtcpMuxPolicy {
+    WebRTCRtcpMuxPolicyNegotiate,
+    WebRTCRtcpMuxPolicyRequire
+};
+
 class WebRTCConfiguration {
 public:
     WebRTCConfiguration() { }
@@ -108,6 +113,8 @@ public:
 
     BLINK_PLATFORM_EXPORT WebRTCBundlePolicy bundlePolicy() const;
 
+    BLINK_PLATFORM_EXPORT WebRTCRtcpMuxPolicy rtcpMuxPolicy() const;
+
 #if INSIDE_BLINK
     BLINK_PLATFORM_EXPORT WebRTCConfiguration(RTCConfiguration*);
 #endif