Add support for metadata on type variables to Fasta parser.

pkg/front_end/lib/src/fasta/source/outline_builder.dart

Index: pkg/front_end/lib/src/fasta/source/outline_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/source/outline_builder.dart b/pkg/front_end/lib/src/fasta/source/outline_builder.dart
index d9ade2c72d4eb4279615194fa671e198b2e77310..d1fb2f17bd19ed27330d2d2a0ab2fc12a6f55917 100644
--- a/pkg/front_end/lib/src/fasta/source/outline_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/outline_builder.dart
@@ -560,6 +560,9 @@ class OutlineBuilder extends UnhandledListener {
     debugEvent("endTypeVariable");
     TypeBuilder bound = pop();
     String name = pop();
+    // TODO(paulberry): type variable metadata should not be ignored.  See
+    // dartbug.com/28981.
+    /* List<MetadataBuilder> metadata = */ pop();
     push(library.addTypeVariable(name, bound, token.charOffset));
   }