Declare TaskTraits for blocking USB tasks in a constexpr

This is the cleanup I suggested in https://crrev.com/2855233002/#msg5 to declare the appropriate task traits for posting blocking tasks in a single place so that there is consistency (and reduced duplication) across //device/usb. BUG=None Review-Url: https://codereview.chromium.org/2864473002 Cr-Commit-Position: refs/heads/master@{#473108}
marcosholgado · May 19, 2017 · 375fc7a · 375fc7a
1 parent 71170cc
commit 375fc7a
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Showing 3 changed files with 14 additions and 10 deletions.
diff --git a/device/usb/usb_service.cc b/device/usb/usb_service.cc
@@ -43,6 +43,9 @@ void UsbService::Observer::OnDeviceRemovedCleanup(
 
 void UsbService::Observer::WillDestroyUsbService() {}
 
+// Declare storage for this constexpr.
+constexpr base::TaskTraits UsbService::kBlockingTaskTraits;
+
 // static
 std::unique_ptr<UsbService> UsbService::Create() {
 #if defined(OS_ANDROID)
@@ -64,9 +67,7 @@ std::unique_ptr<UsbService> UsbService::Create() {
 // static
 scoped_refptr<base::SequencedTaskRunner>
 UsbService::CreateBlockingTaskRunner() {
-  return base::CreateSequencedTaskRunnerWithTraits(
-      {base::MayBlock(), base::TaskPriority::USER_VISIBLE,
-       base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN});
+  return base::CreateSequencedTaskRunnerWithTraits(kBlockingTaskTraits);
 }
 
 UsbService::~UsbService() {

diff --git a/device/usb/usb_service.h b/device/usb/usb_service.h
@@ -18,6 +18,7 @@
 #include "base/observer_list.h"
 #include "base/sequenced_task_runner.h"
 #include "base/single_thread_task_runner.h"
+#include "base/task_scheduler/task_traits.h"
 #include "base/threading/non_thread_safe.h"
 
 namespace device {
@@ -49,10 +50,16 @@ class UsbService : public base::NonThreadSafe {
     virtual void WillDestroyUsbService();
   };
 
+  // These task traits are to be used for posting blocking tasks to the task
+  // scheduler.
+  static constexpr base::TaskTraits kBlockingTaskTraits = {
+      base::MayBlock(), base::TaskPriority::USER_VISIBLE,
+      base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN};
+
   // Returns nullptr when initialization fails.
   static std::unique_ptr<UsbService> Create();
 
-  // Creates a SequencedTaskRunner appropriate for blocking I/O operations.
+  // Creates a SequencedTaskRunner with kBlockingTaskTraits.
   static scoped_refptr<base::SequencedTaskRunner> CreateBlockingTaskRunner();
 
   virtual ~UsbService();

diff --git a/device/usb/usb_service_impl.cc b/device/usb/usb_service_impl.cc
@@ -222,9 +222,7 @@ UsbServiceImpl::UsbServiceImpl()
 #endif
       weak_factory_(this) {
   base::PostTaskWithTraits(
-      FROM_HERE,
-      {base::MayBlock(), base::TaskPriority::USER_VISIBLE,
-       base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},
+      FROM_HERE, kBlockingTaskTraits,
       base::Bind(&InitializeUsbContextOnBlockingThread, task_runner(),
                  base::Bind(&UsbServiceImpl::OnUsbContext,
                             weak_factory_.GetWeakPtr())));
@@ -324,9 +322,7 @@ void UsbServiceImpl::RefreshDevices() {
     pending_path_enumerations_.pop();
   }
 
-  base::PostTaskWithTraits(FROM_HERE,
-                           {base::MayBlock(), base::TaskPriority::USER_VISIBLE,
-                            base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},
+  base::PostTaskWithTraits(FROM_HERE, kBlockingTaskTraits,
                            base::Bind(&GetDeviceListOnBlockingThread,
                                       device_path, context_, task_runner(),
                                       base::Bind(&UsbServiceImpl::OnDeviceList,