Make URLDataSource::GetSource() const.

chrome/browser/ui/webui/ntp/new_tab_ui.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_BROWSER_UI_WEBUI_NTP_NEW_TAB_UI_H_
 #define CHROME_BROWSER_UI_WEBUI_NTP_NEW_TAB_UI_H_
 
 #include <string>
 
 #include "base/gtest_prod_util.h"
@@ skipping 49 matching lines @@
 
   bool showing_sync_bubble() { return showing_sync_bubble_; }
   void set_showing_sync_bubble(bool showing) { showing_sync_bubble_ = showing; }
 
   class NewTabHTMLSource : public content::URLDataSource {
    public:
     explicit NewTabHTMLSource(Profile* profile);
     virtual ~NewTabHTMLSource();
 
     // content::URLDataSource implementation.
-    virtual std::string GetSource() OVERRIDE;
+    virtual std::string GetSource() const OVERRIDE;
     virtual void StartDataRequest(
         const std::string& path,
         bool is_incognito,
         const content::URLDataSource::GotDataCallback& callback) OVERRIDE;
     virtual std::string GetMimeType(const std::string&) const OVERRIDE;
     virtual bool ShouldReplaceExistingSource() const OVERRIDE;
     virtual bool ShouldAddContentSecurityPolicy() const OVERRIDE;
 
     // Adds |resource| to the source. |resource_id| is resource id or 0,
     // which means return empty data set. |mime_type| is mime type of the
@@ skipping 40 matching lines @@
 
   // If the sync promo NTP bubble is being shown.
   bool showing_sync_bubble_;
 
   PrefChangeRegistrar pref_change_registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(NewTabUI);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_NTP_NEW_TAB_UI_H_