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

ash/system/tray_caps_lock.cc

Index: ash/system/tray_caps_lock.cc
diff --git a/ash/system/tray_caps_lock.cc b/ash/system/tray_caps_lock.cc
index a570664abeecf39ca06b446172117a16d7d2c736..7e19eec761243cc986b252b8770249700022bee1 100644
--- a/ash/system/tray_caps_lock.cc
+++ b/ash/system/tray_caps_lock.cc
@@ -118,7 +118,8 @@ bool TrayCapsLock::GetInitialVisibility() {
   return Shell::GetInstance()->caps_lock_delegate()->IsCapsLockEnabled();
 }
 
-views::View* TrayCapsLock::CreateDefaultView(user::LoginStatus status) {
+views::View* TrayCapsLock::CreateDefaultView(user::LoginStatus status,
+                                             int bubble_width) {
   if (!caps_lock_enabled_)
     return NULL;
   DCHECK(default_ == NULL);