[ObjC ARC] Converts ios/web/public/test/fakes:fakes to ARC.

ios/web/public/test/fakes/test_web_state_observer.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.
 
 #include "ios/web/public/test/fakes/test_web_state_observer.h"
 
 #include "base/memory/ptr_util.h"
 #import "ios/web/public/web_state/navigation_context.h"
 #include "ios/web/public/web_state/web_state.h"
 #include "ios/web/web_state/navigation_context_impl.h"
 #include "net/http/http_response_headers.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 TestWebStateObserver::TestWebStateObserver(WebState* web_state)
     : WebStateObserver(web_state) {}
 TestWebStateObserver::~TestWebStateObserver() = default;
 
 void TestWebStateObserver::NavigationItemCommitted(
     const LoadCommittedDetails& load_details) {
   commit_navigation_info_ = base::MakeUnique<web::TestCommitNavigationInfo>();
   commit_navigation_info_->web_state = web_state();
@@ skipping 127 matching lines @@
   start_loading_info_ = base::MakeUnique<web::TestStartLoadingInfo>();
   start_loading_info_->web_state = web_state();
 }
 
 void TestWebStateObserver::DidStopLoading() {
   stop_loading_info_ = base::MakeUnique<web::TestStopLoadingInfo>();
   stop_loading_info_->web_state = web_state();
 }
 
 }  // namespace web