[ios] Add TODO to record usages of "return std::move(foo)" pattern.

ios/chrome/browser/infobars/infobar_utils.mm

 // Copyright 2014 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 "ios/chrome/browser/infobars/infobar_utils.h"
 
 #include <memory>
 #include <utility>
 
 #include "components/infobars/core/confirm_infobar_delegate.h"
 #include "ios/chrome/browser/infobars/confirm_infobar_controller.h"
 #include "ios/chrome/browser/infobars/infobar.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 std::unique_ptr<infobars::InfoBar> CreateConfirmInfoBar(
     std::unique_ptr<ConfirmInfoBarDelegate> delegate) {
   std::unique_ptr<InfoBarIOS> infobar(new InfoBarIOS(std::move(delegate)));
   ConfirmInfoBarController* controller =
       [[ConfirmInfoBarController alloc] initWithDelegate:infobar.get()];
   infobar->SetController(controller);
+  // TODO(crbug.com/703565): remove std::move() once Xcode 9.0+ is required.
   return std::move(infobar);
 }