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 6a9fc420eb6e9258a69428a3f90f5960068a2f4d..aa1fdc0ecab369c93333a2f8f43a316c28470786 100644
--- a/pkg/polymer/lib/src/build/script_compactor.dart
+++ b/pkg/polymer/lib/src/build/script_compactor.dart
@@ -48,8 +48,8 @@ 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));
+  Future<bool> isPrimary(AssetId id) =>
+      new Future.value(options.isHtmlEntryPoint(id));
 
   Future apply(Transform transform) =>
       new _ScriptCompactor(transform, options, resolvers).apply();