Add update available icon in system tray

ash/public/interfaces/system_tray.mojom

 // Copyright 2016 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.
 
 module ash.mojom;
 
 import "ash/public/interfaces/update.mojom";
 import "mojo/common/string16.mojom";
 
 // Allows clients (e.g. Chrome browser) to control the ash system tray menu.
@@ skipping 16 matching lines @@
   // enterprise management. The item appears if |enterprise_domain| is not empty
   // or |active_directory_managed| is true.
   SetEnterpriseDomain(string enterprise_domain, bool active_directory_managed);
 
   // Shows an icon in the system tray indicating that a software update is
   // available. Once shown the icon persists until reboot. |severity| and
   // |factory_reset_required| are used to set the icon, color, and tooltip.
   ShowUpdateIcon(UpdateSeverity severity,
                  bool factory_reset_required,
                  UpdateType update_type);
+
+  // Shows an icon in the system tray indicating that a software update is
+  // available but user's agreement is required as current connection is
+  // cellular. Once shown the icon persists until reboot.
+  ShowUpdateOverCellularAvailableIcon();
 };
 
 // Allows ash system tray to control a client (e.g. Chrome browser). Requests
 // often involve preferences or web UI that is not available to ash.
 interface SystemTrayClient {
   // Shows general settings UI.
   ShowSettings();
 
   // Shows settings related to Bluetooth devices (e.g. to add a device).
   ShowBluetoothSettings();
@@ skipping 18 matching lines @@
 
   // Shows settings related to power.
   ShowPowerSettings();
 
   // Shows the page that lets you disable performance tracing.
   ShowChromeSlow();
 
   // Shows settings related to input methods.
   ShowIMESettings();
 
+  // Show the about chrome OS page.

[stevenjb, 2017/05/16 19:49:06]

Shows

[weidongg, 2017/05/17 00:27:23]

Done.

+  ShowAboutChromeOS();
+
   // Shows help.

[stevenjb, 2017/05/16 19:49:06]

Change this to: // Shows the Chromebook help app.

[weidongg, 2017/05/17 00:27:23]

Done.

   ShowHelp();
 
   // Show accessibility help.
   ShowAccessibilityHelp();
 
   // Show the settings related to accessibility.
   ShowAccessibilitySettings();
 
   // Shows the help center article for the stylus tool palette.
   ShowPaletteHelp();
@@ skipping 28 matching lines @@
 
   // Shows UI for changing proxy settings.
   ShowProxySettings();
 
   // Attempts to sign out the user.
   // TODO(jamescook): Migrate to a user or login service. crbug.com/665582
   SignOut();
 
   // Attempts to restart the system for update.
   RequestRestartForUpdate();
+
+  // Schedule checking for update after about Chrome OS page is loaded.
+  ScheduleRequestUpdateCheck();
 };