Add more tested features to closure_test

tests/compiler/dart2js/equivalence/id_equivalence.dart

Index: tests/compiler/dart2js/equivalence/id_equivalence.dart
diff --git a/tests/compiler/dart2js/equivalence/id_equivalence.dart b/tests/compiler/dart2js/equivalence/id_equivalence.dart
index 749a7b8ebb3ec2cb29d4579f47ebf125353f2f20..c746f6a3e7424e5896916b5ed01d5b09a641fe30 100644
--- a/tests/compiler/dart2js/equivalence/id_equivalence.dart
+++ b/tests/compiler/dart2js/equivalence/id_equivalence.dart
@@ -213,6 +213,10 @@ abstract class IrEnumeratorMixin {
     } else if (node is ir.VariableDeclaration) {
       assert(node.fileOffset != ir.TreeNode.noOffset);
       return new NodeId(node.fileOffset);
+      // TODO(johnniwinther): Enable when function expressions have offsets.
+      /*} else if (node is ir.FunctionExpression) {
+      assert(node.fileOffset != ir.TreeNode.noOffset);
+      return new NodeId(node.fileOffset);*/
     } else if (node is ir.FunctionDeclaration) {
       assert(node.fileOffset != ir.TreeNode.noOffset);
       return new NodeId(node.fileOffset);