Cleanup: Remove unneeded forward declarations from chrome/browser/extensions.

chrome/browser/extensions/extension_sidebar_api.h

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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 CHROME_BROWSER_EXTENSIONS_EXTENSION_SIDEBAR_API_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SIDEBAR_API_H_
 
 #include <string>
 #include "chrome/browser/extensions/extension_function.h"
 
 class Profile;
-class RenderViewHost;
 class TabContents;
 
 namespace base {
 class DictionaryValue;
 }
 
 namespace extension_sidebar_constants {
 extern const char kActiveState[];
 extern const char kHiddenState[];
 extern const char kShownState[];
@@ skipping 87 matching lines @@
 
 class ShowSidebarFunction : public SidebarFunction {
  private:
   virtual bool RunImpl(TabContents* tab,
                        const std::string& content_id,
                        const base::DictionaryValue& details);
   DECLARE_EXTENSION_FUNCTION_NAME("experimental.sidebar.show");
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SIDEBAR_API_H_