Add support for BeforeUnloadEvent

Source/core/dom/Event.h

Index: Source/core/dom/Event.h
diff --git a/Source/core/dom/Event.h b/Source/core/dom/Event.h
index 7875b1e2386ba683ba61e4bf6fec75dd87d1d1bd..399597831bd2c4e2af89d29a9a5f5210e0dde2f6 100644
--- a/Source/core/dom/Event.h
+++ b/Source/core/dom/Event.h
@@ -112,9 +112,6 @@ public:
     // IE Extensions
     EventTarget* srcElement() const { return target(); } // MSIE extension - "the object that fired the event"
 
-    bool returnValue() const { return !defaultPrevented(); }
-    void setReturnValue(bool returnValue) { setDefaultPrevented(!returnValue); }
-
     Clipboard* clipboardData() const { return isClipboardEvent() ? clipboard() : 0; }
 
     virtual const AtomicString& interfaceName() const;
@@ -157,9 +154,6 @@ public:
     EventPath& eventPath() { return m_eventPath; }
     PassRefPtr<NodeList> path() const;
 
-    virtual bool storesResultAsString() const;
-    virtual void storeResult(const String&);
-
     virtual Clipboard* clipboard() const { return 0; }
 
     bool isBeingDispatched() const { return eventPhase(); }