Make URLDataSource::GetSource() const.

chrome/browser/ui/webui/ntp/thumbnail_source.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/ntp/thumbnail_source.h"
 
 #include "base/callback.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/message_loop.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 12 matching lines @@
 
 // Set ThumbnailService now as Profile isn't thread safe.
 ThumbnailSource::ThumbnailSource(Profile* profile)
     : thumbnail_service_(ThumbnailServiceFactory::GetForProfile(profile)),
       profile_(profile) {
 }
 
 ThumbnailSource::~ThumbnailSource() {
 }
 
-std::string ThumbnailSource::GetSource() {
+std::string ThumbnailSource::GetSource() const {
   return chrome::kChromeUIThumbnailHost;
 }
 
 void ThumbnailSource::StartDataRequest(
     const std::string& raw_path,
     bool is_incognito,
     const content::URLDataSource::GotDataCallback& callback) {
   // Translate to regular path if |raw_path| is of the form
   // chrome-search://favicon/<id> or chrome-search://thumb/<id>, where <id> is
   // an integer.
@@ skipping 45 matching lines @@
       if (!MessageLoopForRequestPath(raw_path)) {
         id_to_url_map_[raw_path] =
             InstantService::MaybeTranslateInstantPathOnIO(request, raw_path);
       }
       return true;
     }
     return false;
   }
   return URLDataSource::ShouldServiceRequest(request);
 }