Move the IconLoader to use the task scheduler.

chrome/browser/icon_loader_android.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 "base/logging.h"
 #include "chrome/browser/icon_loader.h"
 
 // static
 IconLoader::IconGroup IconLoader::GroupForFilepath(
     const base::FilePath& file_path) {
   NOTIMPLEMENTED();
   return IconLoader::IconGroup();
 }
 
 // static
-content::BrowserThread::ID IconLoader::ReadIconThreadID() {
+scoped_refptr<base::TaskRunner> IconLoader::GetReadIconTaskRunner() {
   NOTIMPLEMENTED();
-  return content::BrowserThread::FILE;
+  return nullptr;
 }
 
 void IconLoader::ReadIcon() {
   NOTIMPLEMENTED();
   delete this;
 }