VR: Factor transient timing out of UiSceneManager.

chrome/browser/android/vr_shell/ui_elements/presentation_toast.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_PRESENTATION_TOAST_H_
 #define CHROME_BROWSER_ANDROID_VR_SHELL_UI_ELEMENTS_PRESENTATION_TOAST_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "chrome/browser/android/vr_shell/ui_elements/textured_element.h"
+#include "chrome/browser/android/vr_shell/ui_elements/transience_manager.h"
 
 namespace vr_shell {
 
 class UiTexture;
 
 // TODO(bshe): A lot code duplication with exit_warning_texture and
 // insecure_content_transient_texture. Consider refactor(see crbug.com/735166).
 class PresentationToast : public TexturedElement {
  public:
-  explicit PresentationToast(int preferred_width);
+  PresentationToast(int preferred_width, const base::TimeDelta& timeout);
   ~PresentationToast() override;
+  TransienceManager* transience() { return &transience_; }
+
+  // This element manages its own visibility.
+  void SetEnabled(bool enabled) override;
 
  private:
   UiTexture* GetTexture() const override;
 
   std::unique_ptr<UiTexture> texture_;
+  TransienceManager transience_;
 
   DISALLOW_COPY_AND_ASSIGN(PresentationToast);
 };
 
 }  // namespace vr_shell
 
 #endif  // CHROME_BROWSER_ANDROID_VR_SHELL_UI_ELEMENTS_PRESENTATION_TOAST_H_