Test using a global, replacable TaskQueueImpl factory.

webrtc/rtc_base/task_queue.h

Index: webrtc/rtc_base/task_queue.h
diff --git a/webrtc/rtc_base/task_queue.h b/webrtc/rtc_base/task_queue.h
index 218fce9a3b9854529e5683731915b13324aaea25..7d3b7606e247135173c4541f2a52218e345697c0 100644
--- a/webrtc/rtc_base/task_queue.h
+++ b/webrtc/rtc_base/task_queue.h
@@ -15,27 +15,22 @@
 #include <memory>
 #include <queue>
 
-#if defined(WEBRTC_MAC) && !defined(WEBRTC_BUILD_LIBEVENT)
+#if defined(WEBRTC_MAC)
 #include <dispatch/dispatch.h>
 #endif
 
 #include "webrtc/rtc_base/constructormagic.h"
 #include "webrtc/rtc_base/criticalsection.h"
-
-#if defined(WEBRTC_WIN) || defined(WEBRTC_BUILD_LIBEVENT)
-#include "webrtc/rtc_base/platform_thread.h"
-#endif
-
-#if defined(WEBRTC_BUILD_LIBEVENT)
-#include "webrtc/rtc_base/refcountedobject.h"
 #include "webrtc/rtc_base/scoped_ref_ptr.h"
 
-struct event_base;
-struct event;
+#if defined(WEBRTC_WIN)
+#include "webrtc/rtc_base/platform_thread.h"
 #endif
 
 namespace rtc {
 
+class TaskQueueImpl;
+
 // Base interface for asynchronously executed tasks.
 // The interface basically consists of a single function, Run(), that executes
 // on the target queue.  For more details see the Run() method and TaskQueue.
@@ -242,32 +237,7 @@ class LOCKABLE TaskQueue {
   }
 
  private:
-#if defined(WEBRTC_BUILD_LIBEVENT)
-  static void ThreadMain(void* context);
-  static void OnWakeup(int socket, short flags, void* context);  // NOLINT
-  static void RunTask(int fd, short flags, void* context);       // NOLINT
-  static void RunTimer(int fd, short flags, void* context);      // NOLINT
-
-  class ReplyTaskOwner;
-  class PostAndReplyTask;
-  class SetTimerTask;
-
-  typedef RefCountedObject<ReplyTaskOwner> ReplyTaskOwnerRef;
-
-  void PrepareReplyTask(scoped_refptr<ReplyTaskOwnerRef> reply_task);
-
-  struct QueueContext;
-
-  int wakeup_pipe_in_ = -1;
-  int wakeup_pipe_out_ = -1;
-  event_base* event_base_;
-  std::unique_ptr<event> wakeup_event_;
-  PlatformThread thread_;
-  rtc::CriticalSection pending_lock_;
-  std::list<std::unique_ptr<QueuedTask>> pending_ GUARDED_BY(pending_lock_);
-  std::list<scoped_refptr<ReplyTaskOwnerRef>> pending_replies_
-      GUARDED_BY(pending_lock_);
-#elif defined(WEBRTC_MAC)
+#if defined(WEBRTC_MAC)
   struct QueueContext;
   struct TaskContext;
   struct PostTaskAndReplyContext;
@@ -295,7 +265,7 @@ class LOCKABLE TaskQueue {
   std::queue<std::unique_ptr<QueuedTask>> pending_ GUARDED_BY(pending_lock_);
   HANDLE in_queue_;
 #else
-#error not supported.
+  const scoped_refptr<TaskQueueImpl> impl_;
 #endif
 
   RTC_DISALLOW_COPY_AND_ASSIGN(TaskQueue);