Add toWebTextAreaElement

Source/web/WebTextAreaElement.cpp

 /*
  * Copyright (C) 2010 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 38 matching lines @@
 {
     m_private = element;
     return *this;
 }
 
 WebTextAreaElement::operator PassRefPtrWillBeRawPtr<HTMLTextAreaElement>() const
 {
     return toHTMLTextAreaElement(m_private.get());
 }
 
+WebTextAreaElement* toWebTextAreaElement(WebElement* webElement)
+{
+    if (!webElement || !isHTMLTextAreaElement(*webElement->unwrap<Element>()))
+        return 0;
+
+    return static_cast<WebTextAreaElement*>(webElement);
+}
+
 } // namespace blink