Make URLDataSource::GetSource() const.

chrome/browser/ui/webui/screenshot_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 CHROME_BROWSER_UI_WEBUI_SCREENSHOT_SOURCE_H_
 #define CHROME_BROWSER_UI_WEBUI_SCREENSHOT_SOURCE_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 32 matching lines @@
 
   // Common access for the screenshot directory, parameter is set to the
   // requested directory and return value of true is given upon success.
   static bool GetScreenshotDirectory(base::FilePath* directory);
 #endif
 
   // Get the basefilename for screenshots
   static std::string GetScreenshotBaseFilename();
 
   // 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;
 
   // Get the screenshot specified by the given relative path that we've cached
   // from a previous request to the screenshots source.
   // Note: This method strips the query string from the given path.
   ScreenshotDataPtr GetCachedScreenshot(const std::string& screenshot_path);
@@ skipping 53 matching lines @@
   Profile* profile_;
 
   // Key: Relative path to the screenshot (including filename)
   // Value: Pointer to the screenshot data associated with the path.
   std::map<std::string, ScreenshotDataPtr> cached_screenshots_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenshotSource);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SCREENSHOT_SOURCE_H_