Fix unsafeReadProtoTagged so it works in IE

src/DOM/Util/FFI.js

@@ -1,22 +1,27 @@
 "use strict";
 
-exports._unsafeReadProtoTagged = function (name) {
-  return function (failure) {
-    return function (success) {
-      return function (value) {
-        var obj = value;
-        while (obj != null) {
-          var proto = Object.getPrototypeOf(obj);
-          var ctor = proto.constructor.name;
-          if (ctor === name) {
-            return success(value);
-          } else if (ctor === "Object") {
-            return failure(Object.getPrototypeOf(value).constructor.name);
+exports._unsafeReadProtoTagged = (function () {
+  var tagOf = function (value) {
+    return Object.prototype.toString.call(value).slice(8, -1);
+  };
+  return function (name) {
+    return function (failure) {
+      return function (success) {
+        return function (value) {
+          var obj = value;
+          while (obj != null) {
+            var proto = Object.getPrototypeOf(obj);
+            var ctor = tagOf(proto);
+            if (ctor === name) {
+              return success(value);
+            } else if (ctor === "Object") {
+              return failure(tagOf(value));
+            }
+            obj = proto;
           }
-          obj = proto;
-        }
-        return failure(Object.getPrototypeOf(value).constructor.name);
+          return failure(tagOf(value));
+        };
       };
     };
   };
-};
+}());