[ObjC ARC] Converts the rest of ios/web to ARC.

ios/web/web_state/web_state_impl.mm

 // Copyright 2013 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/web/web_state/web_state_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/metrics/histogram_macros.h"
@@ skipping 16 matching lines @@
 #include "ios/web/public/web_state/web_state_policy_decider.h"
 #include "ios/web/web_state/global_web_state_event_tracker.h"
 #import "ios/web/web_state/ui/crw_web_controller.h"
 #import "ios/web/web_state/ui/crw_web_controller_container_view.h"
 #include "ios/web/web_state/web_state_facade_delegate.h"
 #import "ios/web/webui/web_ui_ios_controller_factory_registry.h"
 #import "ios/web/webui/web_ui_ios_impl.h"
 #include "net/http/http_response_headers.h"
 #include "services/service_manager/public/cpp/interface_registry.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 /* static */
 std::unique_ptr<WebState> WebState::Create(const CreateParams& params) {
   std::unique_ptr<WebStateImpl> web_state(
       new WebStateImpl(params.browser_state));
 
   NSString* window_name = nil;
   NSString* opener_id = nil;
   BOOL opened_by_dom = NO;
@@ skipping 87 matching lines @@
 bool WebStateImpl::Configured() const {
   return web_controller_ != nil;
 }
 
 CRWWebController* WebStateImpl::GetWebController() {
   return web_controller_;
 }
 
 void WebStateImpl::SetWebController(CRWWebController* web_controller) {
   [web_controller_ close];
-  web_controller_.reset([web_controller retain]);
+  web_controller_.reset(web_controller);
 }
 
 WebStateFacadeDelegate* WebStateImpl::GetFacadeDelegate() const {
   return facade_delegate_;
 }
 
 void WebStateImpl::SetFacadeDelegate(WebStateFacadeDelegate* facade_delegate) {
   facade_delegate_ = facade_delegate;
 }
 
@@ skipping 545 matching lines @@
     const LoadCommittedDetails& load_details) {
   for (auto& observer : observers_)
     observer.NavigationItemCommitted(load_details);
 }
 
 WebState* WebStateImpl::GetWebState() {
   return this;
 }
 
 }  // namespace web