Test closure data on anonymous local functions

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 c746f6a3e7424e5896916b5ed01d5b09a641fe30..cc0421de795a4c97c0e6178190eabe0f1a3618b6 100644
--- a/tests/compiler/dart2js/equivalence/id_equivalence.dart
+++ b/tests/compiler/dart2js/equivalence/id_equivalence.dart
@@ -213,10 +213,9 @@ 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) {
+    } else if (node is ir.FunctionExpression) {
       assert(node.fileOffset != ir.TreeNode.noOffset);
-      return new NodeId(node.fileOffset);*/
+      return new NodeId(node.fileOffset);
     } else if (node is ir.FunctionDeclaration) {
       assert(node.fileOffset != ir.TreeNode.noOffset);
       return new NodeId(node.fileOffset);