media: add video capture device for ARC++ camera HAL v3

media/capture/video/chromeos/display_rotation_observer.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_CAPTURE_VIDEO_CHROMEOS_DISPLAY_ROTATION_OBSERVER_H_
+#define MEDIA_CAPTURE_VIDEO_CHROMEOS_DISPLAY_ROTATION_OBSERVER_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/single_thread_task_runner.h"
+#include "ui/display/display.h"
+#include "ui/display/display_observer.h"
+#include "ui/display/screen.h"
+
+namespace media {
+
+class DisplayRotationObserver {
+ public:
+  virtual void SetDisplayRotation(const display::Display& display) = 0;
+};
+
+// Registers itself as an observer at |display::Screen::GetScreen()| and
+// forwards rotation change events to the given DisplayRotationObserver on the
+// thread where ScreenObserverDelegate was created.
+class ScreenObserverDelegate
+    : public display::DisplayObserver,
+      public base::RefCountedThreadSafe<ScreenObserverDelegate> {
+ public:
+  ScreenObserverDelegate(
+      DisplayRotationObserver* observer,
+      scoped_refptr<base::SingleThreadTaskRunner> display_task_runner);
+
+  // The user must call RemoveObserver() to drop the reference to |observer_| in
+  // ScreenObserverDelegate before deleting |observer_|.
+  void RemoveObserver();
+
+ private:
+  friend class base::RefCountedThreadSafe<ScreenObserverDelegate>;
+
+  ~ScreenObserverDelegate() override;
+
+  // DisplayObserver implementations.
+  void OnDisplayAdded(const display::Display& /*new_display*/) override;
+  void OnDisplayRemoved(const display::Display& /*old_display*/) override;
+  void OnDisplayMetricsChanged(const display::Display& display,
+                               uint32_t metrics) override;
+
+  void AddObserverOnDisplayThread();
+  void RemoveObserverOnDisplayThread();
+
+  // Post the screen rotation change from the display thread to capture thread
+  void SendDisplayRotation(const display::Display& display);
+  void SendDisplayRotationOnCaptureThread(const display::Display& display);
+
+  DisplayRotationObserver* observer_;
+  // The task runner where the calls to display::Display must be serialized on.
+  const scoped_refptr<base::SingleThreadTaskRunner> display_task_runner_;
+  // The task runner on which the ScreenObserverDelegate is created.
+  const scoped_refptr<base::SingleThreadTaskRunner> delegate_task_runner_;
+  DISALLOW_IMPLICIT_CONSTRUCTORS(ScreenObserverDelegate);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_CAPTURE_VIDEO_CHROMEOS_DISPLAY_ROTATION_OBSERVER_H_