Add WebNotificationTray

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 6e874c03a82b7ebbaf24a51fc380a20a1eec1203..dd901cfe2aa0c9117bfdbe61535348817866dd45 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -71,6 +71,7 @@ class SystemTrayDelegate;
 class SystemTray;
 class UserWallpaperDelegate;
 class VideoDetector;
+class WebNotificationTray;
 class WindowCycleController;
 
 namespace internal {
@@ -293,6 +294,10 @@ class ASH_EXPORT Shell {
 
   SystemTray* system_tray() const { return system_tray_.get(); }
 
+  WebNotificationTray* web_notification_tray() const {
+    return web_notification_tray_.get();
+  }
+
   // Returns the size of the grid.
   int GetGridSize() const;
 
@@ -446,6 +451,9 @@ class ASH_EXPORT Shell {
   // System tray with clock, Wi-Fi signal, etc.
   scoped_ptr<SystemTray> system_tray_;
 
+  // Tray for web notifications.
+  scoped_ptr<WebNotificationTray> web_notification_tray_;
+
   // Used by ash/shell.
   content::BrowserContext* browser_context_;