Compute an incremental patch to JavaScript code.

dart/site/try/poi/patcher.js

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+;(function(orig) {
+  function patcher(main, args) {
+    this.$dart_patch && this.$dart_unsafe_eval.patch($dart_patch);
+    if (orig) {
+      return orig(main, args);
+    } else {
+      return main(args);
+    }
+  }
+  this.dartMainRunner = patcher;
+})(this.dartMainRunner);