Move the IconLoader to use the task scheduler.

chrome/browser/icon_loader.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/icon_loader.h"
 
+#include <utility>
+
 #include "base/bind.h"
+#include "base/task_scheduler/post_task.h"
+#include "base/task_scheduler/task_traits.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "content/public/browser/browser_thread.h"
 
 using content::BrowserThread;
 
 // static
 IconLoader* IconLoader::Create(const base::FilePath& file_path,
                                IconSize size,
                                IconLoadedCallback callback) {
   return new IconLoader(file_path, size, callback);
 }
 
 void IconLoader::Start() {
   target_task_runner_ = base::ThreadTaskRunnerHandle::Get();
 
-  BrowserThread::PostTaskAndReply(
-      BrowserThread::FILE, FROM_HERE,
-      base::BindOnce(&IconLoader::ReadGroup, base::Unretained(this)),
-      base::BindOnce(&IconLoader::OnReadGroup, base::Unretained(this)));
+  base::PostTaskWithTraits(
+      FROM_HERE, traits(),
+      base::BindOnce(&IconLoader::ReadGroup, base::Unretained(this)));
 }
 
 IconLoader::IconLoader(const base::FilePath& file_path,
                        IconSize size,
                        IconLoadedCallback callback)
     : file_path_(file_path), icon_size_(size), callback_(callback) {}
 
 IconLoader::~IconLoader() {}
 
 void IconLoader::ReadGroup() {
   group_ = GroupForFilepath(file_path_);
+
+  ReadIconTaskRunner()->PostTask(
+      FROM_HERE, base::BindOnce(&IconLoader::ReadIcon, base::Unretained(this)));
 }
-
-void IconLoader::OnReadGroup() {
-  BrowserThread::PostTask(
-      ReadIconThreadID(), FROM_HERE,
-      base::BindOnce(&IconLoader::ReadIcon, base::Unretained(this)));
-}