[polymer] fix imports in Dartium if no script is on the main page

pkg/polymer/lib/polymer.html

Index: pkg/polymer/lib/polymer.html
diff --git a/pkg/polymer/lib/polymer.html b/pkg/polymer/lib/polymer.html
index c4df6198c336710cda7a9d311030459ca52d103b..5cbaf7930cf0eeba0d0f2461a5515da01a8134df 100644
--- a/pkg/polymer/lib/polymer.html
+++ b/pkg/polymer/lib/polymer.html
@@ -6,11 +6,6 @@
 
 <script src="src/js/use_native_dartium_shadowdom.js"></script>
 
-<!-- Bootstrap the user application in a new isolate. -->
-<script src="boot.js"></script>
-<!-- TODO(sigmund): replace boot.js by boot.dart (dartbug.com/18007)
-<script type="application/dart">export "package:polymer/boot.dart";</script>
- -->
 <!--
 These two files are from the Polymer project:
 https://github.com/Polymer/platform/ and https://github.com/Polymer/polymer/.
@@ -29,3 +24,9 @@ You can replace platform.js and polymer.html with different versions if desired.
 
 <!-- Teach dart2js about Shadow DOM polyfill objects. -->
 <script src="../../packages/web_components/dart_support.js"></script>
+
+<!-- Bootstrap the user application in a new isolate. -->
+<script src="boot.js"></script>
+<!-- TODO(sigmund): replace boot.js by boot.dart (dartbug.com/18007)
+<script type="application/dart">export "package:polymer/boot.dart";</script>
+ -->