Refactoring: Add toWebFrameImpl() interface.

Source/web/tests/CustomEventTest.cpp

 /*
  * Copyright (C) 2013 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 82 matching lines @@
 // SerializedScriptValue, and that this value can be retrieved and read in an
 // event listener. Initialization of a CustomEvent with a SerializedScriptValue
 // is an internal API, so it cannot be tested with a LayoutTest.
 TEST(CustomEventTest, InitWithSerializedScriptValue)
 {
     const std::string baseURL = "http://www.test.com";
     const std::string path = "visible_iframe.html";
 
     URLTestHelpers::registerMockedURLFromBaseURL(WebString::fromUTF8(baseURL.c_str()), WebString::fromUTF8(path.c_str()));
     WebView* webView = FrameTestHelpers::createWebViewAndLoad(baseURL + path);
-    WebFrameImpl* frame = static_cast<WebFrameImpl*>(webView->mainFrame());
+    WebFrameImpl* frame = toWebFrameImpl(webView->mainFrame());
 
     WebDOMEvent event = frame->frame()->document()->createEvent("CustomEvent", IGNORE_EXCEPTION);
     WebDOMCustomEvent customEvent = event.to<WebDOMCustomEvent>();
 
     v8::HandleScope handleScope;
     customEvent.initCustomEvent("blah", false, false, WebSerializedScriptValue::serialize(v8::Boolean::New(true)));
     RefPtr<EventListener> listener = TestListener::create(frame->mainWorldScriptContext());
     frame->frame()->document()->addEventListener("blah", listener, false);
     frame->frame()->document()->dispatchEvent(event);
 
     Platform::current()->unitTestSupport()->unregisterAllMockedURLs();
     webView->close();
 }
 
 }