Fix printing project on linux.

printing/page_overlays.h

 // Copyright (c) 2006-2009 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_PAGE_OVERLAYS_H_
 #define PRINTING_PAGE_OVERLAYS_H_
 
 #include <string>
 
 namespace printing {
@@ skipping 22 matching lines @@
   PageOverlays();
 
   // Equality operator.
   bool Equals(const PageOverlays& rhs) const;
 
   // Returns the string of an overlay according to its x,y position.
   const std::wstring& GetOverlay(HorizontalPosition x,
                                  VerticalPosition y) const;
 
   // Sets the string of an overlay according to its x,y position.
-  void SetOverlay(HorizontalPosition x, VerticalPosition y,
-                  std::wstring& input);
+  void SetOverlay(HorizontalPosition x,
+                  VerticalPosition y,
+                  const std::wstring& input);
 
   // Replaces the variables in |input| with their actual values according to the
   // properties of the current printed document and the current printed page.
   static std::wstring ReplaceVariables(const std::wstring& input,
                                        const PrintedDocument& document,
                                        const PrintedPage& page);
 
   // Keys that are dynamically replaced in the header and footer by their actual
   // values.
   // Web page's title.
@@ skipping 16 matching lines @@
   std::wstring top_center;
   std::wstring top_right;
   std::wstring bottom_left;
   std::wstring bottom_center;
   std::wstring bottom_right;
 };
 
 }  // namespace printing
 
 #endif  // PRINTING_PAGE_OVERLAYS_H_