Implement WebStorageArea::containsItem(key) in chrome and drt/test_shell.

content/renderer/dom_storage/webstoragearea_impl.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_DOM_STORAGE_WEBSTORAGEAREA_IMPL_H_
 #define CONTENT_RENDERER_DOM_STORAGE_WEBSTORAGEAREA_IMPL_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
@@ skipping 10 matching lines @@
  public:
   static WebStorageAreaImpl* FromConnectionId(int id);
 
   WebStorageAreaImpl(int64 namespace_id, const GURL& origin);
   virtual ~WebStorageAreaImpl();
 
   // See WebStorageArea.h for documentation on these functions.
   virtual unsigned length();
   virtual WebKit::WebString key(unsigned index);
   virtual WebKit::WebString getItem(const WebKit::WebString& key);
+  virtual bool containsItem(const WebKit::WebString& key);
   virtual void setItem(
       const WebKit::WebString& key, const WebKit::WebString& value,
       const WebKit::WebURL& page_url, WebStorageArea::Result& result);
   virtual void removeItem(
       const WebKit::WebString& key, const WebKit::WebURL& page_url);
   virtual void clear(const WebKit::WebURL& url);
 
  private:
   int connection_id_;
   scoped_refptr<dom_storage::DomStorageCachedArea> cached_area_;
 };
 
 #endif  // CONTENT_RENDERER_DOM_STORAGE_WEBSTORAGEAREA_IMPL_H_