Add WebNotificationTray

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index d73d85cf5cb407f5ef0b8c93216861b7b121afd8..87b8a6bb358bc66dbbdce78430dd091f1ca2e885 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -72,6 +72,7 @@ class SystemTrayDelegate;
 class SystemTray;
 class UserWallpaperDelegate;
 class VideoDetector;
+class WebNotificationTray;
 class WindowCycleController;
 
 namespace internal {
@@ -299,6 +300,10 @@ class ASH_EXPORT Shell : aura::CursorDelegate {
 
   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;
 
@@ -457,6 +462,9 @@ class ASH_EXPORT Shell : aura::CursorDelegate {
   // 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_;