Oilpan: switch some leftover raw references over to traced Member<>s.

Source/modules/mediastream/RTCDataChannel.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 86 matching lines @@
     virtual void didReceiveStringData(const WebString&) override;
     virtual void didReceiveRawData(const char*, size_t) override;
     virtual void didDetectError() override;
 
 private:
     RTCDataChannel(ExecutionContext*, RTCPeerConnection*, PassOwnPtr<WebRTCDataChannelHandler>);
 
     void scheduleDispatchEvent(PassRefPtrWillBeRawPtr<Event>);
     void scheduledEventTimerFired(Timer<RTCDataChannel>*);
 
-    ExecutionContext* m_executionContext;
+    RawPtrWillBeMember<ExecutionContext> m_executionContext;
 
     OwnPtr<WebRTCDataChannelHandler> m_handler;
 
     bool m_stopped;
 
     WebRTCDataChannelHandlerClient::ReadyState m_readyState;
 
     enum BinaryType {
         BinaryTypeBlob,
         BinaryTypeArrayBuffer
     };
     BinaryType m_binaryType;
 
     Timer<RTCDataChannel> m_scheduledEventTimer;
     WillBeHeapVector<RefPtrWillBeMember<Event>> m_scheduledEvents;
 
     WeakMember<RTCPeerConnection> m_connection;
 };
 
 } // namespace blink
 
 #endif // RTCDataChannel_h