[ObjC ARC] Converts ios/chrome/test/app:test_support to ARC.

ios/chrome/test/app/web_view_interaction_test_util.mm

Index: ios/chrome/test/app/web_view_interaction_test_util.mm
diff --git a/ios/chrome/test/app/web_view_interaction_test_util.mm b/ios/chrome/test/app/web_view_interaction_test_util.mm
index 4bbf076b4b53c75731e9c08c7d920558ba177c36..b5a12a5fee27bcd5a678e5bf2e6d74bd4e035292 100644
--- a/ios/chrome/test/app/web_view_interaction_test_util.mm
+++ b/ios/chrome/test/app/web_view_interaction_test_util.mm
@@ -7,6 +7,10 @@
 #import "ios/chrome/test/app/chrome_test_util.h"
 #import "ios/web/public/test/web_view_interaction_test_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace chrome_test_util {
 
 void TapWebViewElementWithId(const std::string& element_id) {