Return zone from initPolymer

pkg/polymer/lib/src/loader.dart

Index: pkg/polymer/lib/src/loader.dart
diff --git a/pkg/polymer/lib/src/loader.dart b/pkg/polymer/lib/src/loader.dart
index c999660682762b3a2beb1519f95aef2ea2865c78..eb0a7269c46b61897f9ea52a6e8225981fce697e 100644
--- a/pkg/polymer/lib/src/loader.dart
+++ b/pkg/polymer/lib/src/loader.dart
@@ -32,12 +32,13 @@ const initMethod = const _InitMethodAnnotation();
  * The urls in [libraries] can be absolute or relative to
  * `currentMirrorSystem().isolate.rootLibrary.uri`.
  */
-void initPolymer() {
+Zone initPolymer() {
   if (_useDirtyChecking) {
-    dirtyCheckZone().run(_initPolymerOptimized);
-  } else {
-    _initPolymerOptimized();
+    return dirtyCheckZone()..run(_initPolymerOptimized);
   }
+
+  _initPolymerOptimized();
+  return Zone.current;
 }
 
 /**