VR: Factor transient timing out of UiSceneManager.

chrome/browser/android/vr_shell/ui_elements/transience_manager.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 CHROME_BROWSER_ANDROID_VR_SHELL_UI_ELEMENTS_TRANSIENCE_MANAGER_H_
+#define CHROME_BROWSER_ANDROID_VR_SHELL_UI_ELEMENTS_TRANSIENCE_MANAGER_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "base/timer/timer.h"
+#include "chrome/browser/android/vr_shell/ui_elements/ui_element.h"
+
+namespace vr_shell {
+
+class TransienceManager {
+ public:
+  TransienceManager(UiElement* element, const base::TimeDelta& timeout);
+  virtual ~TransienceManager() = default;
+
+  void SetEnabled(bool enabled);
+  void KickVisibilityIfEnabled();
+  void EndVisibilityIfEnabled();
+
+ private:
+  void StartTimer();
+  void OnTimeout();
+
+  UiElement* element_;
+  base::TimeDelta timeout_;
+  bool enabled_ = false;
+  base::OneShotTimer visibility_timer_;
+};
+
+}  // namespace vr_shell
+
+#endif  // CHROME_BROWSER_ANDROID_VR_SHELL_UI_ELEMENTS_TRANSIENCE_MANAGER_H_