Cleanup: Use base namespace in printing/.

printing/printed_pages_source.h

 // 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 PRINTING_PRINTED_PAGES_SOURCE_H_
 #define PRINTING_PRINTED_PAGES_SOURCE_H_
 
 #include "base/strings/string16.h"
 
 namespace printing {
 
 // Source of printed pages.
 class PrintedPagesSource {
  public:
   // Returns the document title.
-  virtual string16 RenderSourceName() = 0;
+  virtual base::string16 RenderSourceName() = 0;
 
  protected:
   virtual ~PrintedPagesSource() {}
 };
 
 }  // namespace printing
 
 #endif  // PRINTING_PRINTED_PAGES_SOURCE_H_