Update to current webrtc library

This is from the upstream library commit id
3326535126e435f1ba647885ce43a8f0f3d317eb, corresponding to Chromium
88.0.4290.1.

webrtc/api/task_queue/queued_task.h

@@ -0,0 +1,32 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#ifndef API_TASK_QUEUE_QUEUED_TASK_H_
+#define API_TASK_QUEUE_QUEUED_TASK_H_
+
+namespace webrtc {
+
+// 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.
+class QueuedTask {
+ public:
+  virtual ~QueuedTask() = default;
+
+  // Main routine that will run when the task is executed on the desired queue.
+  // The task should return |true| to indicate that it should be deleted or
+  // |false| to indicate that the queue should consider ownership of the task
+  // having been transferred.  Returning |false| can be useful if a task has
+  // re-posted itself to a different queue or is otherwise being re-used.
+  virtual bool Run() = 0;
+};
+
+}  // namespace webrtc
+
+#endif  // API_TASK_QUEUE_QUEUED_TASK_H_

webrtc/api/task_queue/task_queue_base.cc

@@ -0,0 +1,79 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#include "api/task_queue/task_queue_base.h"
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "rtc_base/checks.h"
+
+#if defined(ABSL_HAVE_THREAD_LOCAL)
+
+namespace webrtc {
+namespace {
+
+ABSL_CONST_INIT thread_local TaskQueueBase* current = nullptr;
+
+}  // namespace
+
+TaskQueueBase* TaskQueueBase::Current() {
+  return current;
+}
+
+TaskQueueBase::CurrentTaskQueueSetter::CurrentTaskQueueSetter(
+    TaskQueueBase* task_queue)
+    : previous_(current) {
+  current = task_queue;
+}
+
+TaskQueueBase::CurrentTaskQueueSetter::~CurrentTaskQueueSetter() {
+  current = previous_;
+}
+}  // namespace webrtc
+
+#elif defined(WEBRTC_POSIX)
+
+#include <pthread.h>
+
+namespace webrtc {
+namespace {
+
+ABSL_CONST_INIT pthread_key_t g_queue_ptr_tls = 0;
+
+void InitializeTls() {
+  RTC_CHECK(pthread_key_create(&g_queue_ptr_tls, nullptr) == 0);
+}
+
+pthread_key_t GetQueuePtrTls() {
+  static pthread_once_t init_once = PTHREAD_ONCE_INIT;
+  RTC_CHECK(pthread_once(&init_once, &InitializeTls) == 0);
+  return g_queue_ptr_tls;
+}
+
+}  // namespace
+
+TaskQueueBase* TaskQueueBase::Current() {
+  return static_cast<TaskQueueBase*>(pthread_getspecific(GetQueuePtrTls()));
+}
+
+TaskQueueBase::CurrentTaskQueueSetter::CurrentTaskQueueSetter(
+    TaskQueueBase* task_queue)
+    : previous_(TaskQueueBase::Current()) {
+  pthread_setspecific(GetQueuePtrTls(), task_queue);
+}
+
+TaskQueueBase::CurrentTaskQueueSetter::~CurrentTaskQueueSetter() {
+  pthread_setspecific(GetQueuePtrTls(), previous_);
+}
+
+}  // namespace webrtc
+
+#else
+#error Unsupported platform
+#endif

webrtc/api/task_queue/task_queue_base.h

@@ -0,0 +1,83 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#ifndef API_TASK_QUEUE_TASK_QUEUE_BASE_H_
+#define API_TASK_QUEUE_TASK_QUEUE_BASE_H_
+
+#include <memory>
+
+#include "api/task_queue/queued_task.h"
+#include "rtc_base/system/rtc_export.h"
+#include "rtc_base/thread_annotations.h"
+
+namespace webrtc {
+
+// Asynchronously executes tasks in a way that guarantees that they're executed
+// in FIFO order and that tasks never overlap. Tasks may always execute on the
+// same worker thread and they may not. To DCHECK that tasks are executing on a
+// known task queue, use IsCurrent().
+class RTC_LOCKABLE RTC_EXPORT TaskQueueBase {
+ public:
+  // Starts destruction of the task queue.
+  // On return ensures no task are running and no new tasks are able to start
+  // on the task queue.
+  // Responsible for deallocation. Deallocation may happen syncrhoniously during
+  // Delete or asynchronously after Delete returns.
+  // Code not running on the TaskQueue should not make any assumption when
+  // TaskQueue is deallocated and thus should not call any methods after Delete.
+  // Code running on the TaskQueue should not call Delete, but can assume
+  // TaskQueue still exists and may call other methods, e.g. PostTask.
+  virtual void Delete() = 0;
+
+  // Schedules a task to execute. Tasks are executed in FIFO order.
+  // If |task->Run()| returns true, task is deleted on the task queue
+  // before next QueuedTask starts executing.
+  // When a TaskQueue is deleted, pending tasks will not be executed but they
+  // will be deleted. The deletion of tasks may happen synchronously on the
+  // TaskQueue or it may happen asynchronously after TaskQueue is deleted.
+  // This may vary from one implementation to the next so assumptions about
+  // lifetimes of pending tasks should not be made.
+  virtual void PostTask(std::unique_ptr<QueuedTask> task) = 0;
+
+  // Schedules a task to execute a specified number of milliseconds from when
+  // the call is made. The precision should be considered as "best effort"
+  // and in some cases, such as on Windows when all high precision timers have
+  // been used up, can be off by as much as 15 millseconds.
+  virtual void PostDelayedTask(std::unique_ptr<QueuedTask> task,
+                               uint32_t milliseconds) = 0;
+
+  // Returns the task queue that is running the current thread.
+  // Returns nullptr if this thread is not associated with any task queue.
+  static TaskQueueBase* Current();
+  bool IsCurrent() const { return Current() == this; }
+
+ protected:
+  class CurrentTaskQueueSetter {
+   public:
+    explicit CurrentTaskQueueSetter(TaskQueueBase* task_queue);
+    CurrentTaskQueueSetter(const CurrentTaskQueueSetter&) = delete;
+    CurrentTaskQueueSetter& operator=(const CurrentTaskQueueSetter&) = delete;
+    ~CurrentTaskQueueSetter();
+
+   private:
+    TaskQueueBase* const previous_;
+  };
+
+  // Users of the TaskQueue should call Delete instead of directly deleting
+  // this object.
+  virtual ~TaskQueueBase() = default;
+};
+
+struct TaskQueueDeleter {
+  void operator()(TaskQueueBase* task_queue) const { task_queue->Delete(); }
+};
+
+}  // namespace webrtc
+
+#endif  // API_TASK_QUEUE_TASK_QUEUE_BASE_H_