Remove FOR_EACH_OBSERVER from arc/ since it's being deprecated

ui/arc/notification/arc_custom_notification_item.cc

 // Copyright 2016 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 "ui/arc/notification/arc_custom_notification_item.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/strings/string16.h"
 #include "base/strings/utf_string_conversions.h"
 #include "ui/arc/notification/arc_custom_notification_view.h"
@@ skipping 31 matching lines @@
     message_center::MessageCenter* message_center,
     const std::string& notification_key,
     const AccountId& profile_id)
     : ArcNotificationItem(manager,
                           message_center,
                           notification_key,
                           profile_id) {
 }
 
 ArcCustomNotificationItem::~ArcCustomNotificationItem() {
-  FOR_EACH_OBSERVER(Observer, observers_, OnItemDestroying());
+  for (auto& observer : observers_)
+    observer.OnItemDestroying();
 }
 
 void ArcCustomNotificationItem::UpdateWithArcNotificationData(
     mojom::ArcNotificationDataPtr data) {
   DCHECK(CalledOnValidThread());
   DCHECK_EQ(notification_key(), data->key);
 
   if (HasPendingNotification()) {
     CacheArcNotificationData(std::move(data));
     return;
@@ skipping 23 matching lines @@
 
   pinned_ = rich_data.pinned;
 
   if (!data->snapshot_image || data->snapshot_image->isNull()) {
     snapshot_ = gfx::ImageSkia();
   } else {
     snapshot_ = gfx::ImageSkia(gfx::ImageSkiaRep(
         *data->snapshot_image, data->snapshot_image_scale));
   }
 
-  FOR_EACH_OBSERVER(Observer, observers_, OnItemUpdated());
+  for (auto& observer : observers_)
+    observer.OnItemUpdated();
 
   AddToMessageCenter();
 }
 
 void ArcCustomNotificationItem::CloseFromCloseButton() {
   // Needs to manually remove notification from MessageCenter because
   // the floating close button is not part of MessageCenter.
   message_center()->RemoveNotification(notification_id(), true);
   Close(true);
 }
@@ skipping 13 matching lines @@
 }
 
 void ArcCustomNotificationItem::DecrementWindowRefCount() {
   DCHECK_GT(window_ref_count_, 0);
   --window_ref_count_;
   if (window_ref_count_ == 0)
     manager()->CloseNotificationWindow(notification_key());
 }
 
 }  // namespace arc