Remove non-cros support from ash/common/system.

ash/common/system/web_notification/web_notification_tray.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/common/system/web_notification/web_notification_tray.h"
 
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shelf/shelf_constants.h"
 #include "ash/common/shelf/wm_shelf.h"
@@ skipping 27 matching lines @@
 #include "ui/message_center/views/message_bubble_base.h"
 #include "ui/message_center/views/message_center_bubble.h"
 #include "ui/message_center/views/message_popup_collection.h"
 #include "ui/strings/grit/ui_strings.h"
 #include "ui/views/bubble/tray_bubble_view.h"
 #include "ui/views/controls/image_view.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/controls/menu/menu_runner.h"
 #include "ui/views/layout/fill_layout.h"
 
-#if defined(OS_CHROMEOS)
-
 namespace message_center {
 
 MessageCenterTrayDelegate* CreateMessageCenterTray() {
-  // On Windows+Ash the Tray will not be hosted in ash::Shell.
+  // On non-CrOS, the Tray will not be hosted in ash::Shell.
   NOTREACHED();
   return nullptr;
 }
 
 }  // namespace message_center
 
-#endif  // defined(OS_CHROMEOS)
-
 namespace ash {
 namespace {
 
 // Menu commands
 constexpr int kToggleQuietMode = 0;
 constexpr int kEnableQuietModeDay = 2;
 
 constexpr int kMaximumSmallIconCount = 3;
 
 constexpr gfx::Size kTrayItemInnerIconSize(16, 16);
@@ skipping 599 matching lines @@
 
 message_center::MessageCenterBubble*
 WebNotificationTray::GetMessageCenterBubbleForTest() {
   if (!message_center_bubble())
     return nullptr;
   return static_cast<message_center::MessageCenterBubble*>(
       message_center_bubble()->bubble());
 }
 
 }  // namespace ash