Reland of New task queueing primitive for async tasks: TaskQueue.

webrtc/base/task_queue_posix.h

Index: webrtc/base/task_queue_posix.h
diff --git a/webrtc/base/logging_mac.mm b/webrtc/base/task_queue_posix.h
similarity index 52%
copy from webrtc/base/logging_mac.mm
copy to webrtc/base/task_queue_posix.h
index ffee3541a48245e0179670ce2b013f957bc6b88a..b677b78a38cfb68de2c314bbc54c9ef64d58d82f 100644
--- a/webrtc/base/logging_mac.mm
+++ b/webrtc/base/task_queue_posix.h
@@ -8,15 +8,29 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include "webrtc/base/logging.h"
-
-#import <Foundation/Foundation.h>
+#ifndef WEBRTC_BASE_TASK_QUEUE_POSIX_H_
+#define WEBRTC_BASE_TASK_QUEUE_POSIX_H_
 
+#include <pthread.h>
 
 namespace rtc {
-std::string DescriptionFromOSStatus(OSStatus err) {
-  NSError* error =
-      [NSError errorWithDomain:NSOSStatusErrorDomain code:err userInfo:nil];
-  return error.description.UTF8String;
-}
+
+class TaskQueue;
+
+namespace internal {
+
+class AutoSetCurrentQueuePtr {
+ public:
+  explicit AutoSetCurrentQueuePtr(TaskQueue* q);
+  ~AutoSetCurrentQueuePtr();
+
+ private:
+  TaskQueue* const prev_;
+};
+
+pthread_key_t GetQueuePtrTls();
+
+}  // namespace internal
 }  // namespace rtc
+
+#endif  // WEBRTC_BASE_TASK_QUEUE_POSIX_H_