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

ios/chrome/browser/ui/ntp/most_visited_layout.mm

Index: ios/chrome/browser/ui/ntp/most_visited_layout.mm
diff --git a/ios/chrome/browser/ui/ntp/most_visited_layout.mm b/ios/chrome/browser/ui/ntp/most_visited_layout.mm
index bd0cdfcf3f3715f35c9a1b0bb6da14d578a79208..e77de3c23d3974b20a0d7da14a93ea6219eac062 100644
--- a/ios/chrome/browser/ui/ntp/most_visited_layout.mm
+++ b/ios/chrome/browser/ui/ntp/most_visited_layout.mm
@@ -7,11 +7,15 @@
 #import "ios/chrome/browser/ui/ntp/new_tab_page_header_constants.h"
 #include "ios/chrome/browser/ui/ui_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @implementation MostVisitedLayout
 
 - (NSArray*)layoutAttributesForElementsInRect:(CGRect)rect {
-  NSMutableArray* layoutAttributes = [
-      [[super layoutAttributesForElementsInRect:rect] mutableCopy] autorelease];
+  NSMutableArray* layoutAttributes =
+      [[super layoutAttributesForElementsInRect:rect] mutableCopy];
   UICollectionViewLayoutAttributes* fixedHeaderAttributes = nil;
   NSIndexPath* fixedHeaderIndexPath =
       [NSIndexPath indexPathForItem:0 inSection:0];