Inherit EventTarget interface instead of duplicating its code

Source/core/xml/XMLHttpRequest.h

Index: Source/core/xml/XMLHttpRequest.h
diff --git a/Source/core/xml/XMLHttpRequest.h b/Source/core/xml/XMLHttpRequest.h
index 91011d37059741b9da6f44f7b2302a5acdf22781..8c7e34cb519094025b31cb4589602a5d94aa85b3 100644
--- a/Source/core/xml/XMLHttpRequest.h
+++ b/Source/core/xml/XMLHttpRequest.h
@@ -48,7 +48,7 @@ class SharedBuffer;
 class TextResourceDecoder;
 class ThreadableLoader;
 
-class XMLHttpRequest : public ScriptWrappable, public RefCounted<XMLHttpRequest>, public EventTarget, private ThreadableLoaderClient, public ActiveDOMObject {
+class XMLHttpRequest : public EventTarget, public ScriptWrappable, public RefCounted<XMLHttpRequest>, private ThreadableLoaderClient, public ActiveDOMObject {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassRefPtr<XMLHttpRequest> create(ScriptExecutionContext*, PassRefPtr<SecurityOrigin> = 0);