Add web compat workarounds for ES2015 RegExp semantics

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 98070fb7352766a8ab02136f2ca3868c14deee9c..2f1222197dc8905472084d259188e6daa5145b28 100644
--- a/test/mjsunit/es6/regexp-flags.js
+++ b/test/mjsunit/es6/regexp-flags.js
@@ -50,7 +50,11 @@ assertEquals(4, get_count);
 
 
 function testName(name) {
-  assertThrows(() => RegExp.prototype[name], TypeError);
+  if (name === "sticky") {
+    assertEquals(undefined, RegExp.prototype[name]);
+  } else {
+    assertThrows(() => RegExp.prototype[name], TypeError);
+  }
   assertEquals(
       "get " + name,
       Object.getOwnPropertyDescriptor(RegExp.prototype, name).get.name);