Ensure we run the observable transform on PolymerElement (fixes issue 14942)

pkg/polymer/pubspec.yaml

Index: pkg/polymer/pubspec.yaml
diff --git a/pkg/polymer/pubspec.yaml b/pkg/polymer/pubspec.yaml
index 853824c9851b0bace0572d3dff071d2dd1811c9f..27c068997a5f9838a0ea471a4b0220693193b6d5 100644
--- a/pkg/polymer/pubspec.yaml
+++ b/pkg/polymer/pubspec.yaml
@@ -1,5 +1,5 @@
 name: polymer
-version: 0.9.0
+version: 0.9.1
 author: Polymer.dart Authors <web-ui-dev@dartlang.org>
 description: >
   Polymer.dart is a new type of library for the web, built on top of Web
@@ -16,13 +16,16 @@ dependencies:
   html5lib: ">=0.9.0 <0.10.0"
   html_import: ">=0.9.0 <0.10.0"
   logging: ">=0.9.0 <0.10.0"
-  observe: ">=0.9.0 <0.10.0"
+  observe: ">=0.9.1 <0.10.0"
   path: ">=0.9.0 <0.10.0"
   polymer_expressions: ">=0.9.0 <0.10.0"
   shadow_dom: ">=0.9.0 <0.10.0"
   source_maps: ">=0.9.0 <0.10.0"
   template_binding: ">=0.9.0 <0.10.0"
   yaml: ">=0.9.0 <0.10.0"
+transformers:
+- observe:
+    files: lib/src/instance.dart
 dev_dependencies:
   unittest: ">=0.9.0 <0.10.0"
 environment: