Only pass an AssetId to isPrimary and declareOutputs.

pkg/polymer/lib/src/build/script_compactor.dart

Index: pkg/polymer/lib/src/build/script_compactor.dart
diff --git a/pkg/polymer/lib/src/build/script_compactor.dart b/pkg/polymer/lib/src/build/script_compactor.dart
index dfb25cf5f66e1a42ddfa71701b93696c823c182d..bf8a51dbc920b91a101c1f3573e3c5ea08e50175 100644
--- a/pkg/polymer/lib/src/build/script_compactor.dart
+++ b/pkg/polymer/lib/src/build/script_compactor.dart
@@ -49,8 +49,12 @@ class ScriptCompactor extends Transformer {
       : resolvers = new Resolvers(sdkDir != null ? sdkDir : dartSdkDirectory);
 
   /// Only run on entry point .html files.
-  Future<bool> isPrimary(Asset input) =>
-      new Future.value(options.isHtmlEntryPoint(input.id));
+  // TODO(nweiz): This should just take an AssetId when barback <0.13.0 support
+  // is dropped.
+  Future<bool> isPrimary(idOrAsset) {
+    var id = idOrAsset is AssetId ? idOrAsset : idOrAsset.id;
+    return new Future.value(options.isHtmlEntryPoint(id));
+  }
 
   Future apply(Transform transform) =>
       new _ScriptCompactor(transform, options, resolvers).apply();