fixes #43, remove => workaround

lib/runtime/harmony_feature_check.js

Index: lib/runtime/harmony_feature_check.js
diff --git a/lib/runtime/harmony_feature_check.js b/lib/runtime/harmony_feature_check.js
index 9007bc75d6f8a5b8c704389dccf3b8339ad0a2f3..c2f80e44dd5139a6e15d73f3cb1a0397194c46b5 100644
--- a/lib/runtime/harmony_feature_check.js
+++ b/lib/runtime/harmony_feature_check.js
@@ -9,9 +9,7 @@
       '"use strict";'+
       'class C {' +
         'constructor(x) { this.x = x; };' +
-        // TODO(jmesserly): arrow functions on V8 don't have lexical this yet.
-        // https://code.google.com/p/v8/issues/detail?id=2700
-        '["foo"]() { var self = this; return x => self.x + x; };' +
+        '["foo"]() { return x => this.x + x; };' +
       '};' +
       'return new C(42).foo()(100);');
     if (f() == 142) return; // supported!