Add TaskPriority as a parameter to SequencedWorkerPool in preparation for TaskScheduler experiment.

chrome/service/service_process.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/service/service_process.h"
 
 #include <algorithm>
 
 #include "base/base_switches.h"
 #include "base/callback.h"
@@ skipping 134 matching lines @@
   base::Thread::Options options;
   options.message_loop_type = base::MessageLoop::TYPE_IO;
   io_thread_.reset(new ServiceIOThread("ServiceProcess_IO"));
   file_thread_.reset(new base::Thread("ServiceProcess_File"));
   if (!io_thread_->StartWithOptions(options) ||
       !file_thread_->StartWithOptions(options)) {
     NOTREACHED();
     Teardown();
     return false;
   }
-  blocking_pool_ = new base::SequencedWorkerPool(3, "ServiceBlocking");
+  blocking_pool_ = new base::SequencedWorkerPool(
+      3, "ServiceBlocking", base::TaskPriority::BACKGROUND);

[jam, 2016/06/22 20:17:37]

users will notice if this takes arbitrary long time, i.e. printing jobs won't
print

[gab, 2016/06/22 21:08:56]

Okay changing to USER_VISIBLE to keep it as foreground pooled work (and either
way service processes will not be running TaskScheduler right away).

 
   request_context_getter_ = new ServiceURLRequestContextGetter();
 
   base::FilePath user_data_dir;
   PathService::Get(chrome::DIR_USER_DATA, &user_data_dir);
   base::FilePath pref_path =
       user_data_dir.Append(chrome::kServiceStateFileName);
   service_prefs_.reset(new ServiceProcessPrefs(
       pref_path,
       JsonPrefStore::GetTaskRunnerForFile(pref_path, blocking_pool_.get())
@@ skipping 202 matching lines @@
     } else {
       Shutdown();
     }
   }
 }
 
 ServiceProcess::~ServiceProcess() {
   Teardown();
   g_service_process = NULL;
 }