Only pass an AssetId to isPrimary and declareOutputs.

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

Index: pkg/polymer/lib/src/build/import_inliner.dart
diff --git a/pkg/polymer/lib/src/build/import_inliner.dart b/pkg/polymer/lib/src/build/import_inliner.dart
index f565068f69110ffe2959b4bda4763ec708e4e60f..ee2aee0b87c1de94d118e888bce63f8d3bdb9b23 100644
--- a/pkg/polymer/lib/src/build/import_inliner.dart
+++ b/pkg/polymer/lib/src/build/import_inliner.dart
@@ -244,8 +244,12 @@ class ImportInliner extends Transformer {
   ImportInliner(this.options);
 
   /// 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 _HtmlInliner(options, transform).apply();