Further ES2015 RegExp spec compliance fixes

test/mjsunit/es6/regexp-flags.js

Index: test/mjsunit/es6/regexp-flags.js
diff --git a/test/mjsunit/es6/regexp-flags.js b/test/mjsunit/es6/regexp-flags.js
index ad40c43b69baf4fdfa82eb5c24df012fe177d448..480222d95a815b0821a0537d3206464143fce9d5 100644
--- a/test/mjsunit/es6/regexp-flags.js
+++ b/test/mjsunit/es6/regexp-flags.js
@@ -52,9 +52,10 @@ assertEquals(5, get_count);
 
 
 function testName(name) {
-  // TODO(littledan): For web compatibility, we don't throw an exception,
-  // but ES2015 expects an exception to be thrown from this getter.
-  assertEquals(undefined, RegExp.prototype[name]);
+  // Test for ES2017 RegExp web compatibility semantics
+  // https://github.com/tc39/ecma262/pull/511
+  assertEquals(name === "source" ? "(?:)" : undefined,
+               RegExp.prototype[name]);
   assertEquals(
       "get " + name,
       Object.getOwnPropertyDescriptor(RegExp.prototype, name).get.name);