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diff --git a/dom/media/systemservices/video_engine/tab_capturer.h b/dom/media/systemservices/video_engine/tab_capturer.h
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+++ b/dom/media/systemservices/video_engine/tab_capturer.h
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+/*
+ *  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 MODULES_DESKTOP_CAPTURE_TAB_CAPTURER_H_
+#define MODULES_DESKTOP_CAPTURE_TAB_CAPTURER_H_
+
+#include "api/sequence_checker.h"
+#include "modules/desktop_capture/desktop_capturer.h"
+#include "mozilla/MozPromise.h"
+#include "nsDeque.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla {
+namespace dom {
+struct ImageBitmapCloneData;
+}  // namespace dom
+
+class CaptureFrameRequest;
+class TabCapturedHandler;
+class TaskQueue;
+
+class TabCapturerWebrtc : public webrtc::DesktopCapturer {
+ protected:
+  TabCapturerWebrtc(SourceId aSourceId,
+                    nsCOMPtr<nsISerialEventTarget> aCaptureThread);
+  ~TabCapturerWebrtc();
+
+ public:
+  friend class CaptureFrameRequest;
+  friend class TabCapturedHandler;
+
+  static std::unique_ptr<webrtc::DesktopCapturer> Create(
+      SourceId aSourceId, nsCOMPtr<nsISerialEventTarget> aCaptureThread);
+
+  TabCapturerWebrtc(const TabCapturerWebrtc&) = delete;
+  TabCapturerWebrtc& operator=(const TabCapturerWebrtc&) = delete;
+
+  // DesktopCapturer interface.
+  void Start(Callback* aCallback) override;
+  void CaptureFrame() override;
+  bool GetSourceList(SourceList* aSources) override;
+  bool SelectSource(SourceId) override;
+  bool FocusOnSelectedSource() override;
+  bool IsOccluded(const webrtc::DesktopVector& aPos) override;
+
+ private:
+  // Capture code
+  using CapturePromise =
+      MozPromise<UniquePtr<dom::ImageBitmapCloneData>, nsresult, true>;
+  RefPtr<CapturePromise> CaptureFrameNow();
+
+  // Helper that checks for overrun requests. Returns true if aRequest had not
+  // been dropped due to disconnection or overrun.
+  // Note that if this returns true, the caller takes the responsibility to call
+  // mCallback with a capture result for aRequest.
+  bool CompleteRequest(CaptureFrameRequest* aRequest);
+
+  // Helper that disconnects the request, and notifies mCallback of a temporary
+  // failure.
+  void DisconnectRequest(CaptureFrameRequest* aRequest);
+
+  // Handle the result from the async callback from CaptureFrameNow.
+  void OnCaptureFrameSuccess(UniquePtr<dom::ImageBitmapCloneData> aData);
+  void OnCaptureFrameFailure();
+
+  const uint64_t mBrowserId;
+  const RefPtr<TaskQueue> mMainThreadWorker;
+  const RefPtr<TaskQueue> mCallbackWorker;
+  webrtc::SequenceChecker mControlChecker;
+  webrtc::SequenceChecker mCallbackChecker;
+  // Set in Start() and guaranteed by the owner of this class to outlive us.
+  webrtc::DesktopCapturer::Callback* mCallback
+      RTC_GUARDED_BY(mCallbackChecker) = nullptr;
+
+  // mCallbackWorker only
+  nsRefPtrDeque<CaptureFrameRequest> mRequests RTC_GUARDED_BY(mCallbackChecker);
+};
+
+}  // namespace mozilla
+
+#endif  // MODULES_DESKTOP_CAPTURE_TAB_CAPTURER_H_