Mark some PrintPreviewUI methods as const.

chrome/browser/ui/webui/print_preview/print_preview_handler.cc

 // 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.
 
 #include "chrome/browser/ui/webui/print_preview/print_preview_handler.h"
 
 #include <ctype.h>
 #include <stddef.h>
 
 #include <map>
@@ skipping 1001 matching lines @@
 }
 
 void PrintPreviewHandler::PrintToPdf() {
   if (!print_to_pdf_path_.empty()) {
     // User has already selected a path, no need to show the dialog again.
     PostPrintToPdfTask();
   } else if (!select_file_dialog_.get() ||
              !select_file_dialog_->IsRunning(platform_util::GetTopLevel(
                  preview_web_contents()->GetNativeView()))) {
     // Pre-populating select file dialog with print job title.
-    base::string16 print_job_title_utf16 =
+    const base::string16& print_job_title_utf16 =
         print_preview_ui()->initiator_title();
 
 #if defined(OS_WIN)
     base::FilePath::StringType print_job_title(print_job_title_utf16);
 #elif defined(OS_POSIX)
     base::FilePath::StringType print_job_title =
         base::UTF16ToUTF8(print_job_title_utf16);
 #endif
 
     base::i18n::ReplaceIllegalCharactersInPath(&print_job_title, '_');
@@ skipping 761 matching lines @@
 
 void PrintPreviewHandler::UnregisterForGaiaCookieChanges() {
   if (gaia_cookie_manager_service_)
     gaia_cookie_manager_service_->RemoveObserver(this);
 }
 
 void PrintPreviewHandler::SetPdfSavedClosureForTesting(
     const base::Closure& closure) {
   pdf_file_saved_closure_ = closure;
 }