Use TIMER_SLACK_MAXIMUM on the TaskScheduler service thread.

base/task_scheduler/task_scheduler_impl.cc

 // Copyright 2016 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/task_scheduler/task_scheduler_impl.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 98 matching lines @@
   DCHECK(!worker_pool_index_for_traits_callback_.is_null());
 }
 
 void TaskSchedulerImpl::Initialize(
     const std::vector<SchedulerWorkerPoolParams>& worker_pool_params_vector) {
   DCHECK(!worker_pool_params_vector.empty());
 
   // Start the service thread. On platforms that support it (POSIX except NaCL
   // SFI), the service thread runs a MessageLoopForIO which is used to support
   // FileDescriptorWatcher in the scope in which tasks run.
-  constexpr MessageLoop::Type kServiceThreadMessageLoopType =
+  Thread::Options service_thread_options;
+  service_thread_options.message_loop_type =
 #if defined(OS_POSIX) && !defined(OS_NACL_SFI)
       MessageLoop::TYPE_IO;
 #else
       MessageLoop::TYPE_DEFAULT;
 #endif
-  constexpr size_t kDefaultStackSize = 0;
-  CHECK(service_thread_.StartWithOptions(
-      Thread::Options(kServiceThreadMessageLoopType, kDefaultStackSize)));
+  service_thread_options.timer_slack = TIMER_SLACK_MAXIMUM;
+  CHECK(service_thread_.StartWithOptions(service_thread_options));
 
   // Instantiate TaskTracker. Needs to happen after starting the service thread
   // to get its message_loop().
   task_tracker_ =
 #if defined(OS_POSIX) && !defined(OS_NACL_SFI)
       base::MakeUnique<TaskTrackerPosix>(
           static_cast<MessageLoopForIO*>(service_thread_.message_loop()));
 #else
       base::MakeUnique<TaskTracker>();
 #endif
@@ skipping 39 matching lines @@
   // in |sequence|.
   const TaskTraits traits =
       sequence->PeekTaskTraits().WithPriority(sort_key.priority());
 
   GetWorkerPoolForTraits(traits)->ReEnqueueSequence(std::move(sequence),
                                                     sort_key);
 }
 
 }  // namespace internal
 }  // namespace base