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

ios/chrome/browser/ui/keyboard_commands_egtest.mm

Index: ios/chrome/browser/ui/keyboard_commands_egtest.mm
diff --git a/ios/chrome/browser/ui/keyboard_commands_egtest.mm b/ios/chrome/browser/ui/keyboard_commands_egtest.mm
index e0305e83e2692a92650c7dfe7e6f038553ed3dd7..ae63e64d829c3e1a0499330520fdbd903ca96fe9 100644
--- a/ios/chrome/browser/ui/keyboard_commands_egtest.mm
+++ b/ios/chrome/browser/ui/keyboard_commands_egtest.mm
@@ -24,6 +24,10 @@
 #import "ios/web/public/test/http_server.h"
 #include "ios/web/public/test/http_server_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 const CGFloat kScrollDisplacement = 50.0;
 
 // Test cases to verify that keyboard commands are and are not registered when