[ARC] [Split this CL] Convert ios/web/webui to ARC.

ios/web/webui/mojo_facade.mm

 // Copyright 2016 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/webui/mojo_facade.h"
 
 #import <Foundation/Foundation.h>
 
 #include "base/ios/block_types.h"
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/mac/bind_objc_block.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/values.h"
 #import "ios/web/public/web_state/js/crw_js_injection_evaluator.h"
 #include "ios/web/public/web_thread.h"
 #include "mojo/public/cpp/system/core.h"
 #include "services/shell/public/interfaces/interface_provider.mojom.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 namespace {
 
 // Wraps an integer into |base::Value| as |TYPE_INTEGER|.
 template <typename IntegerT>
 std::unique_ptr<base::Value> ValueFromInteger(IntegerT handle) {
   return std::unique_ptr<base::Value>(
       new base::FundamentalValue(static_cast<int>(handle)));
 }
@@ skipping 228 matching lines @@
 
 std::unique_ptr<base::Value> MojoFacade::HandleSupportCancelWatch(
     const base::DictionaryValue* args) {
   int watch_id = 0;
   CHECK(args->GetInteger("watchId", &watch_id));
   watchers_.erase(watch_id);
   return nullptr;
 }
 
 }  // namespace web