Stop using shell::GetInstance()->system_tray() in system tray items

ash/system/tray_update.cc

Index: ash/system/tray_update.cc
diff --git a/ash/system/tray_update.cc b/ash/system/tray_update.cc
index 2e0e97dd146424d5c3a1e0e7f5202f87930e3f98..50e37ba730b4679c6b0c4209346a0f6433d849f4 100644
--- a/ash/system/tray_update.cc
+++ b/ash/system/tray_update.cc
@@ -164,14 +164,15 @@ bool TrayUpdate::GetInitialVisibility() {
   return Shell::GetInstance()->tray_delegate()->SystemShouldUpgrade();
 }
 
-views::View* TrayUpdate::CreateDefaultView(user::LoginStatus status) {
+views::View* TrayUpdate::CreateDefaultView(user::LoginStatus status,
+                                           int bubble_width) {
   if (!Shell::GetInstance()->tray_delegate()->SystemShouldUpgrade())
     return NULL;
   return new UpdateView(severity_);
 }
 
 views::View* TrayUpdate::CreateDetailedView(user::LoginStatus status) {
-  return CreateDefaultView(status);
+  return CreateDefaultView(status, 0);
 }
 
 void TrayUpdate::DestroyDetailedView() {