Implement time stamp in new-style notification.

ui/message_center/views/notification_header_view.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 UI_MESSAGE_CENTER_VIEWS_NOTIFICATION_HEADER_VIEW_H_
 #define UI_MESSAGE_CENTER_VIEWS_NOTIFICATION_HEADER_VIEW_H_
 
 #include "base/macros.h"
 #include "ui/message_center/views/padded_button.h"
 #include "ui/views/controls/button/custom_button.h"
 
 namespace views {
 class ImageButton;
 class ImageView;
 class Label;
 }
 
 namespace message_center {
 
 class NotificationHeaderView : public views::CustomButton {
  public:
   NotificationHeaderView(views::ButtonListener* listener);
   void SetAppIcon(const gfx::ImageSkia& img);
   void SetAppName(const base::string16& name);
   void SetProgress(int progress);
   void SetOverflowIndicator(int count);
+  void SetTimestamp(base::Time past);
   void SetExpandButtonEnabled(bool enabled);
   void SetExpanded(bool expanded);
   void SetSettingsButtonEnabled(bool enabled);
   void SetCloseButtonEnabled(bool enabled);
   void SetControlButtonsVisible(bool visible);
   void ClearProgress();
   void ClearOverflowIndicator();
+  void ClearTimestamp();
   bool IsExpandButtonEnabled();
   bool IsSettingsButtonEnabled();
   bool IsCloseButtonEnabled();
   bool IsCloseButtonFocused();
 
   // CustomButton override:
   std::unique_ptr<views::InkDrop> CreateInkDrop() override;
   std::unique_ptr<views::InkDropRipple> CreateInkDropRipple() const override;
   std::unique_ptr<views::InkDropHighlight> CreateInkDropHighlight()
       const override;
 
   views::ImageView* expand_button() { return expand_button_; }
   views::ImageButton* settings_button() { return settings_button_; }
   views::ImageButton* close_button() { return close_button_; }
 
  private:
   void UpdateControlButtonsVisibility();
+  // Update visibility for both |summary_text_view_| and |timestamp_view_|.
   void UpdateSummaryTextVisibility();
 
   views::Label* app_name_view_ = nullptr;
   views::Label* summary_text_divider_ = nullptr;
   views::Label* summary_text_view_ = nullptr;
+  views::Label* timestamp_divider_ = nullptr;
+  views::Label* timestamp_view_ = nullptr;
   views::ImageView* app_icon_view_ = nullptr;
   views::ImageView* expand_button_ = nullptr;
   PaddedButton* settings_button_ = nullptr;
   PaddedButton* close_button_ = nullptr;
 
   bool settings_button_enabled_ = false;
   bool close_button_enabled_ = false;
   bool is_control_buttons_visible_ = false;
   bool has_progress_ = false;
   bool has_overflow_indicator_ = false;
+  bool has_timestamp_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(NotificationHeaderView);
 };
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_VIEWS_NOTIFICATION_HEADER_VIEW_H_