Refactoring: Add toWebFrameImpl() interface.

Source/web/WebRange.cpp

 /*
  * 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 98 matching lines @@
 WebRange WebRange::expandedToParagraph() const
 {
     WebRange copy(*this);
     copy.m_private->expand("block", IGNORE_EXCEPTION);
     return copy;
 }
 
 // static
 WebRange WebRange::fromDocumentRange(WebFrame* frame, int start, int length)
 {
-    WebCore::Frame* webFrame = static_cast<WebFrameImpl*>(frame)->frame();
+    WebCore::Frame* webFrame = toWebFrameImpl(frame)->frame();
     Element* selectionRoot = webFrame->selection()->rootEditableElement();
     ContainerNode* scope = selectionRoot ? selectionRoot : webFrame->document()->documentElement();
     return TextIterator::rangeFromLocationAndLength(scope, start, length);
 }
 
 WebVector<WebFloatQuad> WebRange::textQuads() const
 {
     if (isNull())
         return WebVector<WebFloatQuad>();
 
@@ skipping 31 matching lines @@
 
 void WebRange::assign(WebRangePrivate* p)
 {
     // p is already ref'd for us by the caller
     if (m_private)
         m_private->deref();
     m_private = p;
 }
 
 } // namespace WebKit