Add explicit base namespace to string16 users.

chrome/common/extensions/api/file_handlers/file_handlers_parser.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_FILE_HANDLERS_FILE_HANDLERS_PARSER_H_
 #define CHROME_COMMON_EXTENSIONS_API_FILE_HANDLERS_FILE_HANDLERS_PARSER_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 26 matching lines @@
   static const std::vector<FileHandlerInfo>* GetFileHandlers(
       const Extension* extension);
 };
 
 // Parses the "file_handlers" manifest key.
 class FileHandlersParser : public ManifestHandler {
  public:
   FileHandlersParser();
   virtual ~FileHandlersParser();
 
-  virtual bool Parse(Extension* extension, string16* error) OVERRIDE;
+  virtual bool Parse(Extension* extension, base::string16* error) OVERRIDE;
 
  private:
   virtual const std::vector<std::string> Keys() const OVERRIDE;
 
   DISALLOW_COPY_AND_ASSIGN(FileHandlersParser);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_API_FILE_HANDLERS_FILE_HANDLERS_PARSER_H_