An undefined literal should match as an undefined literal.

src/ast/ast.cc

Index: src/ast/ast.cc
diff --git a/src/ast/ast.cc b/src/ast/ast.cc
index 43670ad8a5a2c87c134e41e84bc0384f0d417eb9..c055545c4ef4e715fb33cd4fe731cbe03fdc7cf4 100644
--- a/src/ast/ast.cc
+++ b/src/ast/ast.cc
@@ -64,6 +64,10 @@ bool Expression::IsNullLiteral() const {
 
 
 bool Expression::IsUndefinedLiteral(Isolate* isolate) const {
+  if (IsLiteral() && AsLiteral()->value()->IsUndefined()) {
+    return true;
+  }
+
   const VariableProxy* var_proxy = AsVariableProxy();
   if (var_proxy == NULL) return false;
   Variable* var = var_proxy->var();