Treat non-callable input as null for EventHandler attributes

Source/bindings/v8/V8EventListener.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 37 matching lines @@
     v8::Local<v8::Object> listener = getListenerObject(context);
 
     // Has the listener been disposed?
     if (listener.IsEmpty())
         return v8::Local<v8::Function>();
 
     if (listener->IsFunction())
         return v8::Local<v8::Function>::Cast(listener);
 
     if (listener->IsObject()) {
+        // EventHandler attributes should only accept JS Functions as input.
+        ASSERT(!isAttribute());

[arv (Not doing code reviews), 2013/08/08 14:41:28]

Maybe use ASSERT_WITH_MESSAGE?

         v8::Local<v8::Value> property = listener->Get(v8::String::NewSymbol("handleEvent"));
         // Check that no exceptions were thrown when getting the
         // handleEvent property and that the value is a function.
         if (!property.IsEmpty() && property->IsFunction())
             return v8::Local<v8::Function>::Cast(property);
     }
 
     return v8::Local<v8::Function>();
 }
 
@@ skipping 17 matching lines @@
         return v8::Local<v8::Value>();
 
     if (!frame->script()->canExecuteScripts(AboutToExecuteScript))
         return v8::Local<v8::Value>();
 
     v8::Handle<v8::Value> parameters[1] = { jsEvent };
     return frame->script()->callFunction(handlerFunction, receiver, WTF_ARRAY_LENGTH(parameters), parameters);
 }
 
 } // namespace WebCore