Remove deprecated priority-less SequencedWorkerPool constructor.

chrome/browser/chromeos/arc/arc_process_service.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.
 //
 // The main point of this class is to cache ARC proc nspid<->pid mapping
 // globally. Since the calculation is costly, a dedicated worker thread is
 // used. All read/write of its internal data structure (i.e., the mapping)
 // should be on this thread.
 
 #include "chrome/browser/chromeos/arc/arc_process_service.h"
@@ skipping 22 matching lines @@
 using base::kNullProcessId;
 using base::Process;
 using base::ProcessId;
 using base::SequencedWorkerPool;
 using std::map;
 using std::set;
 using std::vector;
 
 ArcProcessService::ArcProcessService(ArcBridgeService* bridge_service)
     : ArcService(bridge_service),
-      worker_pool_(new SequencedWorkerPool(1, "arc_process_manager")),
+      worker_pool_(new SequencedWorkerPool(1,
+                                           "arc_process_manager",
+                                           base::TaskPriority::USER_BLOCKING)),

[hidehiko, 2016/08/09 05:59:36]

This is ok for me, or can be USER_VISIBLE, to be consistent with the original
code.
There may be a room to lower the priority in a future CL.

Added cylee@ and nya@ for FYI.

[cylee1, 2016/08/09 08:35:41]

USER_VISIBLe looks good to me.

BTW there's an ongoing CL which changes SequencedWorkerPool to Thread. 
https://codereview.chromium.org/2025593003/
So this change is also temporarily.

[gab, 2016/08/09 14:24:06]

Done.

       weak_ptr_factory_(this) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   arc_bridge_service()->process()->AddObserver(this);
   DCHECK(!g_arc_process_service);
   g_arc_process_service = this;
   // Not intended to be used from the creating thread.
   thread_checker_.DetachFromThread();
 }
 
 ArcProcessService::~ArcProcessService() {
@@ skipping 189 matching lines @@
           nspid_to_pid_.find(nspid) != nspid_to_pid_.end())
         nspid_to_pid_[nspid] = pid;
 
       for (ProcessId child_pid : process_tree[pid])
         queue.push(child_pid);
     }
   }
 }
 
 }  // namespace arc