Remove enable Drive offline system tray UI.

ash/system/tray/system_tray.cc

Index: ash/system/tray/system_tray.cc
diff --git a/ash/system/tray/system_tray.cc b/ash/system/tray/system_tray.cc
index 151beaea19a942866ac45e3cdf483ad486ff3c3c..045526c5dd362c25eff4b56fd8c6c1dbf91e8294 100644
--- a/ash/system/tray/system_tray.cc
+++ b/ash/system/tray/system_tray.cc
@@ -49,7 +49,6 @@
 #if defined(OS_CHROMEOS)
 #include "ash/system/chromeos/audio/tray_audio.h"
 #include "ash/system/chromeos/brightness/tray_brightness.h"
-#include "ash/system/chromeos/drive/tray_drive_notice.h"
 #include "ash/system/chromeos/enterprise/tray_enterprise.h"
 #include "ash/system/chromeos/managed/tray_locally_managed_user.h"
 #include "ash/system/chromeos/network/tray_network.h"
@@ -182,7 +181,6 @@ void SystemTray::CreateItems(SystemTrayDelegate* delegate) {
 
 #if defined(OS_CHROMEOS)
   AddTrayItem(new internal::TrayEnterprise(this));
-  AddTrayItem(new internal::TrayDriveNotice(this));
   AddTrayItem(new internal::TrayLocallyManagedUser(this));
   AddTrayItem(new internal::TrayIME(this));
   AddTrayItem(tray_accessibility_);