Add support for priorities in TaskQueue

webrtc/base/task_queue_libevent.cc

Index: webrtc/base/task_queue_libevent.cc
diff --git a/webrtc/base/task_queue_libevent.cc b/webrtc/base/task_queue_libevent.cc
index c80258811fca2ca88e1c0cfbd80ecaba1866784b..f9c622d73ce0a7d067315f0106c341c3ca34890b 100644
--- a/webrtc/base/task_queue_libevent.cc
+++ b/webrtc/base/task_queue_libevent.cc
@@ -61,6 +61,19 @@ void EventAssign(struct event* ev,
   RTC_CHECK_EQ(0, event_base_set(base, ev));
 #endif
 }
+
+ThreadPriority TaskQueuePriorityToThreadPriority(TaskQueue::Priority priority) {
+  switch (priority) {
+    case TaskQueue::HIGH:
+      return kRealtimePriority;
+    case TaskQueue::LOW:
+      return kLowPriority;
+    case TaskQueue::NORMAL:
+    default:
+      break;
+  }
+  return kNormalPriority;
+}
 }  // namespace
 
 struct TaskQueue::QueueContext {
@@ -133,10 +146,13 @@ class TaskQueue::SetTimerTask : public QueuedTask {
   const uint32_t posted_;
 };
 
-TaskQueue::TaskQueue(const char* queue_name)
+TaskQueue::TaskQueue(const char* queue_name, Priority priority /*= NORMAL*/)
     : event_base_(event_base_new()),
       wakeup_event_(new event()),
-      thread_(&TaskQueue::ThreadMain, this, queue_name) {
+      thread_(&TaskQueue::ThreadMain,
+              this,
+              queue_name,
+              TaskQueuePriorityToThreadPriority(priority)) {
   RTC_DCHECK(queue_name);
   int fds[2];
   RTC_CHECK(pipe(fds) == 0);