Explicitly mark first 2 args of addEventListener/removeEventListener as optional

Source/core/events/EventTarget.h

Index: Source/core/events/EventTarget.h
diff --git a/Source/core/events/EventTarget.h b/Source/core/events/EventTarget.h
index f6fa122d8b0d229438813ec2e495249d2b19409f..c1bf895d476ccdb61ed82d4813e756a1f37781ca 100644
--- a/Source/core/events/EventTarget.h
+++ b/Source/core/events/EventTarget.h
@@ -107,7 +107,14 @@ public:
     virtual DOMWindow* toDOMWindow();
     virtual MessagePort* toMessagePort();
 
+    // FIXME: first 2 args to addEventListener and removeEventListener should
+    // be required (per spec), but throwing TypeError breaks legacy content.
+    // http://crbug.com/353484
+    bool addEventListener() { return false; }
+    bool addEventListener(const AtomicString& eventType) { return false; }
     virtual bool addEventListener(const AtomicString& eventType, PassRefPtr<EventListener>, bool useCapture = false);
+    bool removeEventListener() { return false; }
+    bool removeEventListener(const AtomicString& eventType) { return false; }
     virtual bool removeEventListener(const AtomicString& eventType, EventListener*, bool useCapture = false);
     virtual void removeAllEventListeners();
     virtual bool dispatchEvent(PassRefPtr<Event>);