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

ios/chrome/browser/ui/image_util.mm

Index: ios/chrome/browser/ui/image_util.mm
diff --git a/ios/chrome/browser/ui/image_util.mm b/ios/chrome/browser/ui/image_util.mm
index e1f297b47d51d28551e22daee88d2e2f3d536ea6..08c8c1243dadfa4fed7856ce8895184b1662834b 100644
--- a/ios/chrome/browser/ui/image_util.mm
+++ b/ios/chrome/browser/ui/image_util.mm
@@ -9,6 +9,10 @@
 #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