Make spacing between uber tray items consistent with UI spec.

ash/system/tray/system_tray_item.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/system/tray/system_tray_item.h"
 
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray.h"
+#include "ash/system/tray/tray_constants.h"
+#include "ash/system/tray/tray_item_view.h"
+#include "ui/views/controls/label.h"
 #include "ui/views/view.h"
 
 namespace ash {
 
 SystemTrayItem::SystemTrayItem() {
 }
 
 SystemTrayItem::~SystemTrayItem() {
 }
 
@@ skipping 51 matching lines @@
 
 void SystemTrayItem::ShowNotificationView() {
   Shell::GetInstance()->system_tray()->ShowNotificationView(this);
 }
 
 void SystemTrayItem::HideNotificationView() {
   Shell::GetInstance()->system_tray()->HideNotificationView(this);
 }
 
 }  // namespace ash