Move the Mac Task Manager to the new backend code.

chrome/browser/task_management/sampling/task_manager_io_thread_helper.cc

 // Copyright 2015 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/task_management/sampling/task_manager_io_thread_helper.h"
 
 #include "chrome/browser/task_management/sampling/task_manager_impl.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/resource_request_info.h"
 
 namespace task_management {
 
 namespace {
 
 TaskManagerIoThreadHelper* g_io_thread_helper = nullptr;
 
 }  // namespace
 
 IoThreadHelperManager::IoThreadHelperManager() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
   content::BrowserThread::PostTask(
       content::BrowserThread::IO,
       FROM_HERE,
       base::Bind(&TaskManagerIoThreadHelper::CreateInstance));
 }
 
 IoThreadHelperManager::~IoThreadHelperManager() {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  // This may be called at exit time when the main thread is no longer
+  // registered as the UI thread.
+  DCHECK(
+      content::BrowserThread::CurrentlyOn(content::BrowserThread::UI) ||
+      !content::BrowserThread::IsMessageLoopValid(content::BrowserThread::UI));
 
   content::BrowserThread::PostTask(
       content::BrowserThread::IO,
       FROM_HERE,
       base::Bind(&TaskManagerIoThreadHelper::DeleteInstance));
 }
 
 // static
 void TaskManagerIoThreadHelper::CreateInstance() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
@@ skipping 74 matching lines @@
         base::Bind(&TaskManagerIoThreadHelper::OnMultipleBytesReadIO,
                    weak_factory_.GetWeakPtr()),
         base::TimeDelta::FromSeconds(1));
   }
 
   bytes_read_buffer_.push_back(
       BytesReadParam(origin_pid, child_id, route_id, bytes_read));
 }
 
 }  // namespace task_management