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

ios/chrome/browser/ui/side_swipe/side_swipe_util.mm

Index: ios/chrome/browser/ui/side_swipe/side_swipe_util.mm
diff --git a/ios/chrome/browser/ui/side_swipe/side_swipe_util.mm b/ios/chrome/browser/ui/side_swipe/side_swipe_util.mm
index f8a2a0dc160b2ff29c7228f61e6ab512e539c5b9..7a8455e3e6e98662c110cc08dae49a9dcc1f3533 100644
--- a/ios/chrome/browser/ui/side_swipe/side_swipe_util.mm
+++ b/ios/chrome/browser/ui/side_swipe/side_swipe_util.mm
@@ -8,6 +8,10 @@
 
 #include "ios/chrome/browser/ui/rtl_geometry.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 BOOL IsSwipingBack(UISwipeGestureRecognizerDirection direction) {
   if (UseRTLLayout())
     return direction == UISwipeGestureRecognizerDirectionLeft;