Move low battery notification to Message Center.

ash/system/chromeos/power/tray_power.h

 // Copyright (c) 2012 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 ASH_SYSTEM_CHROMEOS_POWER_TRAY_POWER_H_
 #define ASH_SYSTEM_CHROMEOS_POWER_TRAY_POWER_H_
 
 #include "ash/system/chromeos/power/power_status.h"
 #include "ash/system/tray/system_tray_item.h"
 
 class SkBitmap;
 
 namespace gfx {
 class Image;
 class ImageSkia;
 }
 
 namespace message_center {
 class MessageCenter;
 }
 
 namespace ash {
+
+class BatteryNotification;
+
 namespace tray {
-class PowerNotificationView;
 class PowerTrayView;
 }
 
 class ASH_EXPORT TrayPower : public SystemTrayItem,
                              public PowerStatus::Observer {
  public:
-  // Visible for testing.
   enum NotificationState {
     NOTIFICATION_NONE,
 
     // Low battery charge.
     NOTIFICATION_LOW_POWER,
 
     // Critically low battery charge.
     NOTIFICATION_CRITICAL,
   };
 
@@ skipping 21 matching lines @@
     MAINS_CHARGER,
     USB_CHARGER,
     UNCONFIRMED_SPRING_CHARGER,
     SAFE_SPRING_CHARGER,
     CHARGER_TYPE_COUNT,
   };
 
   // Overridden from SystemTrayItem.
   views::View* CreateTrayView(user::LoginStatus status) override;
   views::View* CreateDefaultView(user::LoginStatus status) override;
-  views::View* CreateNotificationView(user::LoginStatus status) override;
   void DestroyTrayView() override;
   void DestroyDefaultView() override;
-  void DestroyNotificationView() override;
   void UpdateAfterLoginStatusChange(user::LoginStatus status) override;
   void UpdateAfterShelfAlignmentChange(ShelfAlignment alignment) override;
 
   // Overridden from PowerStatus::Observer.
   void OnPowerStatusChanged() override;
 
   // Show a notification that a low-power USB charger has been connected.
   // Returns true if a notification was shown or explicitly hidden.
   bool MaybeShowUsbChargerNotification();
 
   // Sets |notification_state_|. Returns true if a notification should be shown.
   bool UpdateNotificationState();
   bool UpdateNotificationStateForRemainingTime();
   bool UpdateNotificationStateForRemainingPercentage();
 
   message_center::MessageCenter* message_center_;  // Not owned.
   tray::PowerTrayView* power_tray_;
-  tray::PowerNotificationView* notification_view_;
+  scoped_ptr<BatteryNotification> battery_notification_;

[Mr4D (OOO till 08-26), 2015/03/17 17:04:37]

Practically you do not need a scoped_ptr here - couldn't you add the variable
directly? (BatteryNotification battery_notification_;)

[michaelpg, 2015/03/17 18:32:46]

Hmm. I had trouble including battery_notification.h because it depends on this
file for the NotificationState enum. It doesn't look like we allow C++11 forward
declaration of enums. Am I missing a simple way of resolving the this dependency
issue?

I thought about moving the enum to BatteryNotification. In fact, maybe all the
logic about when to show a notification belongs in BatteryNotification as it
doesn't directly relate to the tray anymore. WDYT? 

[Mr4D (OOO till 08-26), 2015/03/17 22:25:04]

That makes sense! Please do!

[michaelpg, 2015/03/17 23:10:39]

Took another look. TrayPower uses NotificationState to determine when to update
the tray view. I wonder if maybe PowerStatus would be a better place, but I
don't want to add more UI specifics there.

However, maybe a scoped pointer actually works. Why should we keep the
BatteryNotification around when we're not using it? And why instantiate one on
startup unless the battery is low?

BatteryNotification is basically a wrapper around a help function for creating a
notification. Instead of using Show/Hide, we can just create/remove the
notification in the constructor/destructor. Take a look at let me know again
what you think - thanks!

[Mr4D (OOO till 08-26), 2015/03/20 03:10:53]

Okay. Now with your changes it makes sense. Thanks!

   NotificationState notification_state_;
 
   // Was a USB charger connected the last time OnPowerStatusChanged() was
   // called?
   bool usb_charger_was_connected_;
 
   // Was line power connected the last time onPowerStatusChanged() was called?
   bool line_power_was_connected_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayPower);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_POWER_TRAY_POWER_H_