[ios] Move WebStateList to ios/chrome/browser/web_state_list.

ios/shared/chrome/browser/tabs/web_state_opener.mm

-// Copyright 2017 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/shared/chrome/browser/tabs/web_state_opener.h"
-
-#include "base/logging.h"
-#import "ios/web/public/navigation_manager.h"
-#import "ios/web/public/web_state/web_state.h"
-
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
-namespace {
-int NavigationIndexFromWebState(web::WebState* web_state) {
-  if (!web_state)
-    return -1;
-
-  DCHECK(web_state->GetNavigationManager());
-  return web_state->GetNavigationManager()->GetLastCommittedItemIndex();
-}
-}  // namespace
-
-WebStateOpener::WebStateOpener(web::WebState* opener)
-    : WebStateOpener(opener, NavigationIndexFromWebState(opener)) {}
-
-WebStateOpener::WebStateOpener(web::WebState* opener, int navigation_index)
-    : opener(opener), navigation_index(navigation_index) {}