[strong] Implement static restrictions on binding 'undefined' in arrow functions

test/mjsunit/strong/undefined.js

Index: test/mjsunit/strong/undefined.js
diff --git a/test/mjsunit/strong/undefined.js b/test/mjsunit/strong/undefined.js
index 8fc213d198ff79b7f9e43a93c2cd2287dd2d2014..28ed02d56e07e327bb479597ea12b1932e306b25 100644
--- a/test/mjsunit/strong/undefined.js
+++ b/test/mjsunit/strong/undefined.js
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --strong-mode --harmony-sloppy --harmony-arrow-functions
+// Flags: --strong-mode --harmony-sloppy
 
 // Repurposing the strict mode 'eval' and 'arguments' tests to test for correct
 // behaviour of 'undefined' as an identifier in strong mode.
@@ -107,11 +107,6 @@ assertThrows("({ foo(a, b, undefined, c, d) {'use strong';} });", SyntaxError);
 CheckStrongMode("({ *foo(a, b, undefined, c, d) {} });");
 assertThrows("({ *foo(a, b, undefined, c, d) {'use strong';} });", SyntaxError);
 
-// Arrow function expression with 'undefined' param
-// TODO(conradw): Checking arrow function heads is hard to modify just now
-// CheckStrongMode("(undefined => {})");
-// assertThrows("(undefined => {'use strong';})");
-
 // Class declaration named 'undefined'
 CheckStrongMode("class undefined {}");
 assertThrows("class undefined {'use strong'}", SyntaxError);