Add update available icon in system tray

chrome/browser/upgrade_detector.h

Index: chrome/browser/upgrade_detector.h
diff --git a/chrome/browser/upgrade_detector.h b/chrome/browser/upgrade_detector.h
index bc8542c8a9dd7335691449bdf129286fba556ca6..56b3129e0fe75b936d8bf40e94d4ebc69855a00c 100644
--- a/chrome/browser/upgrade_detector.h
+++ b/chrome/browser/upgrade_detector.h
@@ -7,6 +7,7 @@
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
+#include "base/observer_list.h"
 #include "base/timer/timer.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "ui/base/idle/idle.h"
@@ -26,6 +27,15 @@ class PrefRegistrySimple;
 //
 class UpgradeDetector {
  public:
+  class UpgradeObserver {

[sky, 2017/05/18 23:41:56]

Remove this to it's own file (see chromium style guide).

[weidongg, 2017/05/19 01:29:53]

Done.

+   public:
+    virtual ~UpgradeObserver();

[sky, 2017/05/18 23:41:56]

Move to protected section, also you can inline this (style guide allows it).

[weidongg, 2017/05/19 01:29:53]

Done.

+
+    // Triggered when a software update is available, but downloading requires
+    // user's agreement as current connection is cellular.
+    virtual void OnUpdateOverCellularAvailable() = 0;
+  };
+
   // The Homeland Security Upgrade Advisory System.
   enum UpgradeNotificationAnnoyanceLevel {
     UPGRADE_ANNOYANCE_NONE = 0,  // What? Me worry?
@@ -79,6 +89,10 @@ class UpgradeDetector {
     return upgrade_notification_stage_;
   }
 
+  void AddObserver(UpgradeObserver* observer);
+
+  void RemoveObserver(UpgradeObserver* observer);
+
  protected:
   enum UpgradeAvailable {
     // If no update is available and current install is recent enough.
@@ -101,6 +115,11 @@ class UpgradeDetector {
   // Sends out UPGRADE_RECOMMENDED notification and set notify_upgrade_.
   void NotifyUpgradeRecommended();
 
+  // The function that sends out a notification that lets the rest of the UI
+  // know we should notify the user that a new update is available to download
+  // over cellular connection.
+  void NotifyUpdateOverCellularAvailable();
+
   // Triggers a critical update, which starts a timer that checks the machine
   // idle state. Protected and virtual so that it could be overridden by tests.
   virtual void TriggerCriticalUpdate();
@@ -175,6 +194,8 @@ class UpgradeDetector {
   // is we should start nagging about upgrading).
   bool notify_upgrade_;
 
+  base::ObserverList<UpgradeObserver> observer_list_;
+
   DISALLOW_COPY_AND_ASSIGN(UpgradeDetector);
 };