Correct iOS build for latest Xcode beta.

ios/web/browsing_data_managers/crw_cookie_browsing_data_manager.mm

 // 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.
 
 #import "ios/web/browsing_data_managers/crw_cookie_browsing_data_manager.h"
 
 #import "base/logging.h"
 #include "ios/web/public/browser_state.h"
 
 @implementation CRWCookieBrowsingDataManager {
   web::BrowserState* _browserState;  // Weak, owns this object.
 }
 
 - (instancetype)initWithBrowserState:(web::BrowserState*)browserState {
   self = [super init];
   if (self) {
     DCHECK(browserState);
     _browserState = browserState;
   }
   return self;
 }
 
+- (instancetype)init {
+  NOTREACHED();
+  return nil;
+}
+
 #pragma mark CRWBrowsingDataManager implementation
 // TODO(shreyasv): During implementation of the following methods evaluate if
 // the entire BrowserState is required. Looks like only |state_path| may be
 // required.
 
 - (void)stashData {
   // TODO(shreyasv): Implement this. crbug.com/480654
 }
 
 - (void)restoreData {
   // TODO(shreyasv): Implement this. crbug.com/480654
 }
 
 - (void)removeDataAtStashPath {
   // TODO(shreyasv): Implement this. crbug.com/480654
 }
 
 - (void)removeDataAtCanonicalPath {
   // TODO(shreyasv): Implement this. crbug.com/480654
 }
 
 @end