Replace URLDataSource::MessageLoopForRequestPath() with TaskRunnerForRequestPath().

chrome/browser/thumbnails/thumbnail_list_source.cc

Index: chrome/browser/thumbnails/thumbnail_list_source.cc
diff --git a/chrome/browser/thumbnails/thumbnail_list_source.cc b/chrome/browser/thumbnails/thumbnail_list_source.cc
index 8dc3d5d064136a9fe07c1c3993d8fefdc62a95c7..7966ac0e793807ed50546cd4301c3db728bf99fa 100644
--- a/chrome/browser/thumbnails/thumbnail_list_source.cc
+++ b/chrome/browser/thumbnails/thumbnail_list_source.cc
@@ -101,7 +101,7 @@ void ThumbnailListSource::StartDataRequest(
     const content::URLDataSource::GotDataCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (!top_sites_) {
-    callback.Run(NULL);
+    callback.Run(nullptr);
     return;
   }
 
@@ -115,11 +115,12 @@ std::string ThumbnailListSource::GetMimeType(const std::string& path) const {
   return "text/html";
 }
 
-base::MessageLoop* ThumbnailListSource::MessageLoopForRequestPath(
-    const std::string& path) const {
+scoped_refptr<base::SingleThreadTaskRunner>
+ThumbnailListSource::TaskRunnerForRequestPath(const std::string& path) const {
   // TopSites can be accessed from the IO thread.
-  return thumbnail_service_.get() ?
-      NULL : content::URLDataSource::MessageLoopForRequestPath(path);
+  return thumbnail_service_.get()
+             ? nullptr
+             : content::URLDataSource::TaskRunnerForRequestPath(path);
 }
 
 bool ThumbnailListSource::ShouldServiceRequest(