Revert of WebStateList is an array of web::WebState* wrappers.

ios/shared/chrome/browser/tabs/web_state_list.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_list.h"
-
-#include "base/logging.h"
-
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
-@implementation WebStateList {
-  NSMutableArray<id<WebStateHandle>>* _list;
-}
-
-#pragma mark - Lifecycle
-
-- (instancetype)init {
-  if ((self = [super init])) {
-    _list = [[NSMutableArray alloc] init];
-  }
-  return self;
-}
-
-#pragma mark - NSFastEnumeration
-
-- (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState*)state
-                                  objects:(id __unsafe_unretained*)buffer
-                                    count:(NSUInteger)len {
-  return [_list countByEnumeratingWithState:state objects:buffer count:len];
-}
-
-#pragma mark - Properties
-
-- (NSUInteger)count {
-  return _list.count;
-}
-
-- (id<WebStateHandle>)firstWebState {
-  return _list.firstObject;
-}
-
-#pragma mark - Public methods, mutation
-
-- (void)addWebState:(id<WebStateHandle>)webState {
-  [_list addObject:webState];
-}
-
-- (void)insertWebState:(id<WebStateHandle>)webState atIndex:(NSUInteger)index {
-  [_list insertObject:webState atIndex:index];
-}
-
-- (void)replaceWebStateAtIndex:(NSUInteger)index
-                  withWebState:(id<WebStateHandle>)webState {
-  [_list replaceObjectAtIndex:index withObject:webState];
-}
-
-- (void)removeWebState:(id<WebStateHandle>)webState {
-  [_list removeObject:webState];
-}
-
-#pragma mark - Public methods, queries
-
-- (BOOL)containsWebState:(id<WebStateHandle>)webState {
-  return [_list containsObject:webState];
-}
-
-- (id<WebStateHandle>)webStateAtIndex:(NSUInteger)index {
-  DCHECK_LT(index, _list.count);
-  return [_list objectAtIndex:index];
-}
-
-- (NSUInteger)indexOfWebState:(id<WebStateHandle>)webState {
-  return [_list indexOfObject:webState];
-}
-
-@end