fixes #314, super method tear offs

lib/runtime/_classes.js

Index: lib/runtime/_classes.js
diff --git a/lib/runtime/_classes.js b/lib/runtime/_classes.js
index 80ceb56249bf4fa36dca9b9729e255d701391dfd..630906455a3d66afcab5ab95fb6b7ffc98386172 100644
--- a/lib/runtime/_classes.js
+++ b/lib/runtime/_classes.js
@@ -193,8 +193,11 @@ dart_library.library('dart_runtime/_classes', null, /* Imports */[
   /// Sets the runtime type of the torn off method appropriately,
   /// and also binds the object.
   /// TODO(leafp): Consider caching the tearoff on the object?
-  function bind(obj, name) {
-    let f = obj[name].bind(obj);
+  function bind(obj, name, f) {

[Leaf, 2015/09/10 17:42:41]

Update the comment to describe the role of f?

[Jennifer Messerly, 2015/09/10 19:23:08]

Nice catch! Done!

+    if (f === void 0) f = obj[name];
+    f = f.bind(obj);
+    // TODO(jmesserly): track the function's signature on the function, instead
+    // of having to go back to the class?
     let sig = _getMethodType(obj, name);
     assert(sig);
     rtti.tag(f, sig);