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

ios/chrome/browser/autocomplete/in_memory_url_index_factory.cc

 // Copyright 2015 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/autocomplete/in_memory_url_index_factory.h"
 
 #include <utility>
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/core/service_access_type.h"
@@ skipping 21 matching lines @@
 
   // Do not force creation of the HistoryService if saving history is disabled.
   std::unique_ptr<InMemoryURLIndex> in_memory_url_index(new InMemoryURLIndex(
       ios::BookmarkModelFactory::GetForBrowserState(browser_state),
       ios::HistoryServiceFactory::GetForBrowserState(
           browser_state, ServiceAccessType::IMPLICIT_ACCESS),
       ios::TemplateURLServiceFactory::GetForBrowserState(browser_state),
       web::WebThread::GetBlockingPool(), browser_state->GetStatePath(),
       schemes_to_whilelist));
   in_memory_url_index->Init();
+  // TODO(crbug.com/703565): remove std::move() once Xcode 9.0+ is required.
   return std::move(in_memory_url_index);
 }
 
 }  // namespace
 
 // static
 InMemoryURLIndex* InMemoryURLIndexFactory::GetForBrowserState(
     ios::ChromeBrowserState* browser_state) {
   return static_cast<InMemoryURLIndex*>(
       GetInstance()->GetServiceForBrowserState(browser_state, true));
@@ skipping 29 matching lines @@
 web::BrowserState* InMemoryURLIndexFactory::GetBrowserStateToUse(
     web::BrowserState* context) const {
   return GetBrowserStateRedirectedInIncognito(context);
 }
 
 bool InMemoryURLIndexFactory::ServiceIsNULLWhileTesting() const {
   return true;
 }
 
 }  // namespace ios