Add explicit base namespace to string16 users.

chrome/common/extensions/api/plugins/plugins_handler.h

 // Copyright (c) 2013 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_PLUGINS_PLUGINS_HANDLER_H_
 #define CHROME_COMMON_EXTENSIONS_API_PLUGINS_PLUGINS_HANDLER_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 18 matching lines @@
   // Return true if the given |extension| has plugins, and false otherwise.
   static bool HasPlugins(const Extension* extension);
 };
 
 // Parses the "plugins" manifest key.
 class PluginsHandler : public ManifestHandler {
  public:
   PluginsHandler();
   virtual ~PluginsHandler();
 
-  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(PluginsHandler);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_API_PLUGINS_PLUGINS_HANDLER_H_