[ObjC ARC] Converts ios/chrome/browser/web:eg_tests to ARC.

ios/chrome/browser/web/navigation_egtest.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 <XCTest/XCTest.h>
 
 #include "base/ios/ios_util.h"
 #include "components/strings/grit/components_strings.h"
 #include "ios/chrome/test/app/web_view_interaction_test_util.h"
 #import "ios/chrome/test/earl_grey/chrome_earl_grey.h"
 #import "ios/chrome/test/earl_grey/chrome_matchers.h"
 #import "ios/chrome/test/earl_grey/chrome_test_case.h"
 #import "ios/web/public/test/http_server.h"
 #include "ios/web/public/test/http_server_util.h"
 #include "ios/web/public/test/response_providers/data_response_provider.h"
 #include "ui/base/l10n/l10n_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using chrome_test_util::BackButton;
 using chrome_test_util::ForwardButton;
 using chrome_test_util::TapWebViewElementWithId;
 using chrome_test_util::WebViewContainingText;
 
 namespace {
 
 // URL for the test window.history.go() test file.  The page at this URL
 // contains several buttons that trigger window.history commands.  Additionally
 // the page contains several divs used to display the state of the page:
@@ skipping 606 matching lines @@
 
 - (void)addHashChangeListenerWithContent:(std::string)content {
   NSString* const script =
       [NSString stringWithFormat:
                     @"document.body.innerHTML = '%s';"
                      "window.addEventListener('hashchange', function(event) {"
                      "   document.body.innerHTML = '%s';"
                      "});",
                     kNoHashChangeText, content.c_str()];
 
-  NSError* error = nil;
+  __unsafe_unretained NSError* error = nil;
   chrome_test_util::ExecuteJavaScript(script, &error);
 }
 
 - (void)verifyBackAndForwardAfterRedirect:(std::string)redirectLabel {
   const GURL indexURL(web::test::HttpServer::MakeUrl(kRedirectIndexURL));
   const GURL destinationURL(web::test::HttpServer::MakeUrl(kDestinationURL));
   const GURL lastURL(web::test::HttpServer::MakeUrl(kLastURL));
 
   // Load index, tap on redirect link, and assert that the page is redirected
   // to the proper destination.
@@ skipping 20 matching lines @@
   // Navigate forward and assert the the resulting page is the proper
   // destination.
   [[EarlGrey selectElementWithMatcher:ForwardButton()]
       performAction:grey_tap()];
   [[EarlGrey selectElementWithMatcher:chrome_test_util::OmniboxText(
                                           destinationURL.GetContent())]
       assertWithMatcher:grey_notNil()];
 }
 
 @end