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 992ae78f2fe9770fb1e67347bb4aea9d5003dbda..548d0b617b302835ac21d4ae8c81839a272d144a 100644
--- a/pkg/polymer/lib/src/build/import_inliner.dart
+++ b/pkg/polymer/lib/src/build/import_inliner.dart
@@ -251,8 +251,8 @@ 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));
+  Future<bool> isPrimary(AssetId id) =>
+      new Future.value(options.isHtmlEntryPoint(id));
 
   Future apply(Transform transform) =>
       new _HtmlInliner(options, transform).apply();