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diff --git a/dom/media/systemservices/video_engine/platform_uithread.h b/dom/media/systemservices/video_engine/platform_uithread.h
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+++ b/dom/media/systemservices/video_engine/platform_uithread.h
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+/*
+ *  Copyright (c) 2015 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 RTC_BASE_PLATFORM_UITHREAD_H_
+#define RTC_BASE_PLATFORM_UITHREAD_H_
+
+#if defined(WEBRTC_WIN)
+#  include "Assertions.h"
+#  include "rtc_base/deprecated/recursive_critical_section.h"
+#  include "rtc_base/platform_thread.h"
+#  include "api/sequence_checker.h"
+#  include "ThreadSafety.h"
+
+namespace rtc {
+/*
+ * Windows UI thread for screen capture
+ * Launches a thread which enters a message wait loop after calling the
+ * provided ThreadRunFunction once. A repeating timer event might be registered
+ * with a callback through the Win32 API. If so, that timer will cause WM_TIMER
+ * messages to appear in the threads message queue. This will wake the thread
+ * which will then first look to see if it received the WM_QUIT message, then
+ * it will pass any non WM_QUIT messages on to the registered message handlers
+ * (synchronously on the current thread). In the case oF WM_TIMER the
+ * registered handler calls the NativeEventCallback which is simply the
+ * ThreadRunFunction which was passed to the constructor.
+ *
+ * Shutdown of the message wait loop is triggered by sending a WM_CLOSE which
+ * will start tearing down the "window" which hosts the UI thread. This will
+ * cause a WM_DESTROY message to be received. Upon reception a WM_QUIT message
+ * is enqueued. When the message wait loop receives a WM_QUIT message it stops,
+ * thus allowing the thread to be joined.
+ *
+ * Note: that the only source of a WM_CLOSE should be PlatformUIThread::Stop.
+ * Note: because PlatformUIThread::Stop is called from a different thread than
+ * PlatformUIThread::Run, it is possible that Stop can race Run.
+ *
+ * After being stopped PlatformUIThread can not be started again.
+ *
+ */
+
+class PlatformUIThread {
+ public:
+  PlatformUIThread(std::function<void()> func, const char* name,
+                   ThreadAttributes attributes)
+      : name_(name),
+        native_event_callback_(std::move(func)),
+        monitor_thread_(PlatformThread::SpawnJoinable([this]() { Run(); }, name,
+                                                      attributes)) {}
+
+  virtual ~PlatformUIThread();
+
+  void Stop();
+
+  /**
+   * Request a recurring callback.
+   */
+  bool RequestCallbackTimer(unsigned int milliseconds);
+
+ protected:
+  void Run();
+
+ private:
+  static LRESULT CALLBACK EventWindowProc(HWND, UINT, WPARAM, LPARAM);
+  void NativeEventCallback();
+  // Initialize the UI thread that is servicing the timer events
+  bool InternalInit();
+
+  // Needs to be initialized before monitor_thread_ as it takes a string view to
+  // name_
+  std::string name_;
+  RecursiveCriticalSection cs_;
+  std::function<void()> native_event_callback_;
+  webrtc::SequenceChecker thread_checker_;
+  PlatformThread monitor_thread_;
+  HWND hwnd_ MOZ_GUARDED_BY(cs_) = nullptr;
+  UINT_PTR timerid_ MOZ_GUARDED_BY(cs_) = 0;
+  unsigned int timeout_ MOZ_GUARDED_BY(cs_) = 0;
+  enum class State {
+    UNSTARTED,
+    STARTED,
+    STOPPED,
+  };
+  State state_ MOZ_GUARDED_BY(cs_) = State::UNSTARTED;
+};
+
+}  // namespace rtc
+
+#endif
+#endif  // RTC_BASE_PLATFORM_UITHREAD_H_