Cleanup: Add conversion interface for WebWidget derived classes.

Source/web/WebPopupMenuImpl.h

 /*
  * Copyright (C) 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 68 matching lines @@
         const WebString& text,
         const WebVector<WebCompositionUnderline>& underlines,
         int selectionStart, int selectionEnd) OVERRIDE;
     virtual bool confirmComposition() OVERRIDE;
     virtual bool confirmComposition(ConfirmCompositionBehavior selectionBehavior) OVERRIDE;
     virtual bool confirmComposition(const WebString& text) OVERRIDE;
     virtual bool compositionRange(size_t* location, size_t* length) OVERRIDE;
     virtual bool caretOrSelectionRange(size_t* location, size_t* length) OVERRIDE;
     virtual void setTextDirection(WebTextDirection) OVERRIDE;
     virtual bool isAcceleratedCompositingActive() const OVERRIDE { return false; }
+    virtual bool isPopupMenu() const OVERRIDE { return true; }
 
     // WebPopupMenuImpl
     void initialize(WebCore::FramelessScrollView* widget, const WebRect& bounds);
 
     WebWidgetClient* client() { return m_client; }
 
     void handleMouseMove(const WebMouseEvent&);
     void handleMouseLeave(const WebMouseEvent&);
     void handleMouseDown(const WebMouseEvent&);
     void handleMouseUp(const WebMouseEvent&);
@@ skipping 28 matching lines @@
     WebWidgetClient* m_client;
     WebSize m_size;
 
     WebPoint m_lastMousePosition;
 
     // This is a non-owning ref. The popup will notify us via popupClosed()
     // before it is destroyed.
     WebCore::FramelessScrollView* m_widget;
 };
 
+inline WebPopupMenuImpl* toWebPopupMenuImpl(WebWidget* widget)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!widget || widget->isPopupMenu());
+    return static_cast<WebPopupMenuImpl*>(widget);
+}
+
+inline WebPopupMenuImpl* toWebPopupMenuImpl(WebCore::FramelessScrollViewClient* client)
+{
+    // WebPopupMenuImpl is the only implementation of FramelessScrollViewClient,
+    // so no need for further checking.
+    return static_cast<WebPopupMenuImpl*>(client);
+}
+
 } // namespace WebKit
 
 #endif