Base the right RegExp brand checks on Symbol.match

test/mjsunit/es6/string-endswith.js

Index: test/mjsunit/es6/string-endswith.js
diff --git a/test/mjsunit/es6/string-endswith.js b/test/mjsunit/es6/string-endswith.js
index cbf2ed87666bdc981a52cf4943d0500a0b249ecf..4246f166a4fc04015729993a7f0024a4c7b1ec85 100644
--- a/test/mjsunit/es6/string-endswith.js
+++ b/test/mjsunit/es6/string-endswith.js
@@ -408,3 +408,11 @@ assertThrows(function() {
     "toString": function() { return "abc"; }
   }, [/./]);
 }, TypeError);
+
+// endsWith does its brand checks with Symbol.match
+var re = /./;
+assertThrows(function() {
+  "".startsWith(re);
+}, TypeError);
+re[Symbol.match] = false;
+assertEquals(false, "".startsWith(re));