Converts parts of ios/web to ARC

ios/web/browser_state.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/public/browser_state.h"
 
 #include "base/location.h"
 #include "base/memory/ref_counted.h"
 #include "ios/web/active_state_manager_impl.h"
 #include "ios/web/public/certificate_policy_cache.h"
 #include "ios/web/public/web_thread.h"
 #include "ios/web/webui/url_data_manager_ios_backend.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 namespace {
 // Private key used for safe conversion of base::SupportsUserData to
 // web::BrowserState in web::BrowserState::FromSupportsUserData.
 const char kBrowserStateIdentifierKey[] = "BrowserStateIdentifierKey";
 
 // Data key names.
 const char kCertificatePolicyCacheKeyName[] = "cert_policy_cache";
 const char kActiveStateManagerKeyName[] = "active_state_manager";
 
@@ skipping 81 matching lines @@
 // static
 BrowserState* BrowserState::FromSupportsUserData(
     base::SupportsUserData* supports_user_data) {
   if (!supports_user_data ||
       !supports_user_data->GetUserData(kBrowserStateIdentifierKey)) {
     return nullptr;
   }
   return static_cast<BrowserState*>(supports_user_data);
 }
 }  // namespace web