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

ios/chrome/browser/ui/ui_util.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/chrome/browser/ui/ui_util.h"
 
 #import <UIKit/UIKit.h>
 
 #include "base/logging.h"
 #import "ios/chrome/browser/ui/uikit_ui_util.h"
 #include "ui/gfx/ios/uikit_util.h"
 
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
 bool IsIPadIdiom() {
   UIUserInterfaceIdiom idiom = [[UIDevice currentDevice] userInterfaceIdiom];
   return idiom == UIUserInterfaceIdiomPad;
 }
 
 const CGFloat kPortraitWidth[INTERFACE_IDIOM_COUNT] = {
     320,  // IPHONE_IDIOM
     768   // IPAD_IDIOM
 };
 
@@ skipping 121 matching lines @@
       projectTo.size = targetSize;
       break;
   }
 
   projectTo = CGRectIntegral(projectTo);
   // There's no CGSizeIntegral, faking one instead.
   CGRect integralRect = CGRectZero;
   integralRect.size = targetSize;
   targetSize = CGRectIntegral(integralRect).size;
 }