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

ios/web/public/test/web_view_interaction_test_util.mm

 // 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.
 
 #import "ios/web/public/test/web_view_interaction_test_util.h"
 
 #import "base/mac/bind_objc_block.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #import "base/test/ios/wait_util.h"
@@ skipping 34 matching lines @@
   }
 
   // As result is marked __block, this return call does a copy and not a move
   // (marking the variable as __block mean it is allocated in the block object
   // and not the stack). Since the "return std::move()" pattern is discouraged
   // use a local variable.
   //
   // Fixes the following compilation failure:
   //   ../web_view_matchers.mm:ll:cc: error: call to implicitly-deleted copy
   //       constructor of 'std::unique_ptr<base::Value>'
+  // TODO(crbug.com/703565): remove std::move() once Xcode 9.0+ is required.
   std::unique_ptr<base::Value> stack_result = std::move(result);
   return stack_result;
 }
 
 CGRect GetBoundingRectOfElementWithId(web::WebState* web_state,
                                       const std::string& element_id) {
   std::string kGetBoundsScript =
       "(function() {"
       "  var element = document.getElementById('" +
       element_id +
@@ skipping 102 matching lines @@
 }
 
 bool SubmitWebViewFormWithId(web::WebState* web_state,
                              const std::string& form_id) {
   return RunActionOnWebViewElementWithId(web_state, form_id,
                                          ELEMENT_ACTION_SUBMIT);
 }
 
 }  // namespace test
 }  // namespace web