[Media controls] Add rotate-to-fullscreen gesture behind flag

third_party/WebKit/Source/modules/media_controls/MediaControlsRotateToFullscreenDelegate.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 MediaControlsRotateToFullscreenDelegate_h
+#define MediaControlsRotateToFullscreenDelegate_h
+
+#include "core/events/EventListener.h"
+#include "modules/ModulesExport.h"
+
+namespace blink {
+
+class HTMLVideoElement;
+class ElementVisibilityObserver;
+
+// MediaControlsRotateToFullscreenDelegate automatically enters and exits
+// fullscreen when the device is rotated whilst watching a <video>. It is meant
+// to be created by `MediaControlsImpl` when the feature applies. Once created,
+// it will listen for events.
+class MediaControlsRotateToFullscreenDelegate final : public EventListener {
+ public:
+  explicit MediaControlsRotateToFullscreenDelegate(HTMLVideoElement&);
+
+  // Called by MediaControlsImpl when the HTMLMediaElement is added to a
+  // document. All event listeners should be added.
+  void Attach();
+
+  // Called by MediaControlsImpl when the HTMLMediaElement is no longer in the
+  // document. All event listeners should be removed in order to prepare the
+  // object to be garbage collected.
+  void Detach();
+
+  // EventListener implementation.
+  bool operator==(const EventListener&) const override;
+
+  DECLARE_VIRTUAL_TRACE();
+
+ private:
+  friend class MediaControlsRotateToFullscreenDelegateTest;
+
+  // Represents either screen orientation or video aspect ratio.
+  enum class SimpleOrientation { kPortrait, kLandscape, kUnknown };
+
+  // EventListener implementation.
+  void handleEvent(ExecutionContext*, Event*) override;
+
+  void OnStateChange();
+  void OnVisibilityChange(bool is_visible);
+  void OnScreenOrientationChange();
+
+  MODULES_EXPORT SimpleOrientation ComputeVideoOrientation() const;
+  SimpleOrientation ComputeScreenOrientation() const;
+
+  SimpleOrientation current_screen_orientation_ = SimpleOrientation::kUnknown;
+
+  // Only valid when visibility_observer_ is active and the first
+  // OnVisibilityChanged has been received; otherwise assume video is hidden.
+  bool is_visible_ = false;
+
+  // This is null whenever we're not listening.
+  Member<ElementVisibilityObserver> visibility_observer_ = nullptr;
+
+  // `video_element_` owns MediaControlsImpl that owns |this|.
+  Member<HTMLVideoElement> video_element_;
+};
+
+}  // namespace blink
+
+#endif  // MediaControlsRotateToFullscreenDelegate_h