Add explicit base namespace to string16 users.

chrome/common/extensions/webview_handler.h

 // Copyright 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_WEBVIEW_HANDLER_H_
 #define CHROME_COMMON_EXTENSIONS_WEBVIEW_HANDLER_H_
 
 #include <string>
 
 #include "extensions/common/extension.h"
@@ skipping 22 matching lines @@
   std::vector<std::string> webview_privileged_partitions_;
   URLPatternSet webview_accessible_resources_;
 };
 
 // Parses the "webview" manifest key.
 class WebviewHandler : public ManifestHandler {
  public:
   WebviewHandler();
   virtual ~WebviewHandler();
 
-  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(WebviewHandler);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_WEBVIEW_HANDLER_H_