Use constexpr TaskTraits constructor in device.

device/usb/usb_service_impl.cc

 // Copyright 2014 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 "device/usb/usb_service_impl.h"
 
 #include <stdint.h>
 
 #include <list>
 #include <memory>
@@ skipping 207 matching lines @@
 }  // namespace
 
 UsbServiceImpl::UsbServiceImpl()
     : UsbService(nullptr),
 #if defined(OS_WIN)
       device_observer_(this),
 #endif
       weak_factory_(this) {
   base::PostTaskWithTraits(
       FROM_HERE,
-      base::TaskTraits()
-          .MayBlock()
-          .WithPriority(base::TaskPriority::USER_VISIBLE)
-          .WithShutdownBehavior(
-              base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN),
+      {base::MayBlock(), base::TaskPriority::USER_VISIBLE,
+       base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},
       base::Bind(&InitializeUsbContextOnBlockingThread, task_runner(),
                  base::Bind(&UsbServiceImpl::OnUsbContext,
                             weak_factory_.GetWeakPtr())));
 }
 
 UsbServiceImpl::~UsbServiceImpl() {
   if (hotplug_enabled_)
     libusb_hotplug_deregister_callback(context_->context(), hotplug_handle_);
   for (auto* platform_device : ignored_devices_)
     libusb_unref_device(platform_device);
@@ skipping 79 matching lines @@
 
   enumeration_in_progress_ = true;
   DCHECK(devices_being_enumerated_.empty());
 
   std::string device_path;
   if (!pending_path_enumerations_.empty()) {
     device_path = pending_path_enumerations_.front();
     pending_path_enumerations_.pop();
   }
 
-  base::PostTaskWithTraits(
-      FROM_HERE,
-      base::TaskTraits()
-          .MayBlock()
-          .WithPriority(base::TaskPriority::USER_VISIBLE)
-          .WithShutdownBehavior(
-              base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN),
-      base::Bind(&GetDeviceListOnBlockingThread, device_path, context_,
-                 task_runner(),
-                 base::Bind(&UsbServiceImpl::OnDeviceList,
-                            weak_factory_.GetWeakPtr())));
+  base::PostTaskWithTraits(FROM_HERE,
+                           {base::MayBlock(), base::TaskPriority::USER_VISIBLE,
+                            base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},

[Reilly Grant (use Gerrit), 2017/05/03 20:27:00]

Since these are the same traits I use in UsbService::CreateBlockingTaskRunner
can you define these as a static constexpr there so that I can simply refer to
them here?

[fdoray, 2017/05/03 20:45:44]

This would indeed be a nice improvement but in the context of automated mass
refactoring we do not have the bandwidth for such per file changes and leave it
up to the owners to fix up local tweaks.

+                           base::Bind(&GetDeviceListOnBlockingThread,
+                                      device_path, context_, task_runner(),
+                                      base::Bind(&UsbServiceImpl::OnDeviceList,
+                                                 weak_factory_.GetWeakPtr())));
 }
 
 void UsbServiceImpl::OnDeviceList(libusb_device** platform_devices,
                                   size_t device_count) {
   DCHECK(CalledOnValidThread());
   if (!platform_devices) {
     RefreshDevicesComplete();
     return;
   }
 
@@ skipping 209 matching lines @@
 }
 
 void UsbServiceImpl::EnumerationFailed(PlatformUsbDevice platform_device,
                                        const base::Closure& refresh_complete) {
   libusb_ref_device(platform_device);
   ignored_devices_.insert(platform_device);
   refresh_complete.Run();
 }
 
 }  // namespace device