ensure window.Polymer is an object. This allows proper manipulation o…

…f it via extend.

src/boot.js

@@ -4,8 +4,15 @@
  * license that can be found in the LICENSE file.
  */
 
-(function(scope) {
 
+// TODO(sorvell): this ensures Polymer is an object and not a function
+// Platform is currently defining it as a function to allow for async loading
+// of polymer; once we refine the loading process this likely goes away.
+if (typeof window.Polymer === 'function') {
+  Polymer = {};
+}
+
+(function(scope) {
   // FOUC prevention tactic
   // default list of veiled elements
   scope.veiledElements = ['body'];