Add explicit base namespace to string16 users.

chrome/common/extensions/api/extension_action/browser_action_handler.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 CHROME_COMMON_EXTENSIONS_API_EXTENSION_ACTION_BROWSER_ACTION_HANDLER_H_
 #define CHROME_COMMON_EXTENSIONS_API_EXTENSION_ACTION_BROWSER_ACTION_HANDLER_H_
 
 #include <string>
 
 #include "chrome/common/extensions/api/extension_action/action_info.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest_handler.h"
 
 namespace extensions {
 
 // Parses the "browser_action" manifest key.
 class BrowserActionHandler : public ManifestHandler {
  public:
   BrowserActionHandler();
   virtual ~BrowserActionHandler();
 
-  virtual bool Parse(Extension* extension, string16* error) OVERRIDE;
+  virtual bool Parse(Extension* extension, base::string16* error) OVERRIDE;
   virtual bool Validate(const Extension* extension,
                         std::string* error,
                         std::vector<InstallWarning>* warnings) const OVERRIDE;
 
  private:
   virtual const std::vector<std::string> Keys() const OVERRIDE;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserActionHandler);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_API_EXTENSION_ACTION_BROWSER_ACTION_HANDLER_H_