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

ios/chrome/browser/ui/image_util.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 <UIKit/UIKit.h>
 
 #import "ios/chrome/browser/ui/image_util.h"
 
 #include "ui/gfx/color_analysis.h"
 #include "ui/gfx/image/image.h"
 
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
 UIColor* DominantColorForImage(const gfx::Image& image, CGFloat opacity) {
   SkColor color = color_utils::CalculateKMeanColorOfBitmap(*image.ToSkBitmap());
   UIColor* result = [UIColor colorWithRed:SkColorGetR(color) / 255.0
                                     green:SkColorGetG(color) / 255.0
                                      blue:SkColorGetB(color) / 255.0
                                     alpha:opacity];
   return result;
 }
 
 UIImage* StretchableImageFromUIImage(UIImage* image,
@@ skipping 17 matching lines @@
 
 UIImage* StretchableImageNamed(NSString* name,
                                NSInteger left_cap_width,
                                NSInteger top_cap_height) {
   UIImage* image = [UIImage imageNamed:name];
   if (!image)
     return nil;
 
   return StretchableImageFromUIImage(image, left_cap_width, top_cap_height);
 }