[ObjC ARC] Converts ios/chrome/browser/ui:ui_internal_arc to ARC.

ios/chrome/browser/ui/chrome_web_view_factory.mm

 // Copyright 2012 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/chrome/browser/ui/chrome_web_view_factory.h"
 
 #include "base/base64.h"
 #include "base/logging.h"
-#include "base/mac/scoped_nsobject.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #include "ios/web/net/request_group_util.h"
 #include "ios/web/net/request_tracker_impl.h"
 #include "ios/web/public/web_thread.h"
 #include "net/cookies/cookie_store.h"
 #include "net/url_request/url_request_context.h"
 #include "net/url_request/url_request_context_getter.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 NSString* const kExternalUserAgent = @"UIWebViewForExternalContent";
 
 namespace ChromeWebView {
 // Shared desktop user agent used to mimic Safari on a mac.
 NSString* const kDesktopUserAgent =
     @"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_4) "
     @"AppleWebKit/600.7.12 (KHTML, like Gecko) "
     @"Version/8.0.7 "
     @"Safari/600.7.12";
 
@@ skipping 126 matching lines @@
   if (!g_request_tracker.get()) {
     DCHECK(g_external_browser_state);
     g_request_tracker = web::RequestTrackerImpl::CreateTrackerForRequestGroupID(
         ChromeWebView::kExternalRequestGroupID, g_external_browser_state,
         [self requestContextForExternalService:externalService], nil);
   }
   return [[UIWebView alloc] initWithFrame:CGRectZero];
 }
 
 @end