Add serializers to RTCIceCandidate and RTCSessionDescription

Source/modules/mediastream/RTCSessionDescription.h

Index: Source/modules/mediastream/RTCSessionDescription.h
diff --git a/Source/modules/mediastream/RTCSessionDescription.h b/Source/modules/mediastream/RTCSessionDescription.h
index 56e2f5596f44f3d87ebe6a1cb411ae25ca11b53c..2ef5d77cf9e5c3273e5746f9ec1f4dbda533ac65 100644
--- a/Source/modules/mediastream/RTCSessionDescription.h
+++ b/Source/modules/mediastream/RTCSessionDescription.h
@@ -38,6 +38,8 @@
 namespace blink {
 
 class RTCSessionDescriptionInit;
+class ScriptState;
+class ScriptValue;
 
 class RTCSessionDescription final : public GarbageCollectedFinalized<RTCSessionDescription>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
@@ -51,6 +53,8 @@ public:
     String sdp();
     void setSdp(const String&);
 
+    ScriptValue toJSONForBinding(ScriptState*);
+
     WebRTCSessionDescription webSessionDescription();
 
     DEFINE_INLINE_TRACE() { }