Move isPrimary computation from PhaseInput into TransformNode.

pkg/barback/test/transformer/lazy_rewrite.dart

Index: pkg/barback/test/transformer/lazy_rewrite.dart
diff --git a/pkg/barback/test/transformer/lazy_rewrite.dart b/pkg/barback/test/transformer/lazy_rewrite.dart
index 61c00e595efec4bcc000088fb8331c50618fd975..f694a0e77da6fd95176075593ed1be8179661b34 100644
--- a/pkg/barback/test/transformer/lazy_rewrite.dart
+++ b/pkg/barback/test/transformer/lazy_rewrite.dart
@@ -18,6 +18,7 @@ class LazyRewriteTransformer extends RewriteTransformer
       : super(from, to);
 
   Future declareOutputs(DeclaringTransform transform) {
+    if (consumePrimary) transform.consumePrimary();
     for (var extension in to.split(" ")) {
       var id = transform.primaryInput.id.changeExtension(".$extension");
       transform.declareOutput(id);