Inherit EventTarget interface instead of duplicating its code

Source/modules/mediastream/RTCPeerConnection.h

Index: Source/modules/mediastream/RTCPeerConnection.h
diff --git a/Source/modules/mediastream/RTCPeerConnection.h b/Source/modules/mediastream/RTCPeerConnection.h
index 502cdb481c6115d130d84a963f432b5211599be4..d582f3d1a325b7e445736d928488e0b8d54ddc90 100644
--- a/Source/modules/mediastream/RTCPeerConnection.h
+++ b/Source/modules/mediastream/RTCPeerConnection.h
@@ -57,7 +57,7 @@ class VoidCallback;
 
 typedef int ExceptionCode;
 
-class RTCPeerConnection : public RefCounted<RTCPeerConnection>, public ScriptWrappable, public RTCPeerConnectionHandlerClient, public EventTarget, public ActiveDOMObject {
+class RTCPeerConnection : public EventTarget, public RefCounted<RTCPeerConnection>, public ScriptWrappable, public RTCPeerConnectionHandlerClient, public ActiveDOMObject {
 public:
     static PassRefPtr<RTCPeerConnection> create(ScriptExecutionContext*, const Dictionary& rtcConfiguration, const Dictionary& mediaConstraints, ExceptionCode&);
     ~RTCPeerConnection();