Undefined is not a literal.

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index 78b7843d991d5479c5ec72d4f8229b43b56cdb9c..f14156f93c6235582325d7894be735c43cb69290 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -353,8 +353,8 @@ class Expression: public AstNode {
   // True iff the expression is the null literal.
   bool IsNullLiteral();
 
-  // True iff the expression is the undefined literal.
-  bool IsUndefinedLiteral();
+  // True if we can prove that the expression is the undefined literal.
+  bool IsUndefinedLiteral(Isolate* isolate);
 
   // Expression type bounds
   Bounds bounds() { return bounds_; }
@@ -1994,7 +1994,7 @@ class CompareOperation: public Expression {
 
   // Match special cases.
   bool IsLiteralCompareTypeof(Expression** expr, Handle<String>* check);
-  bool IsLiteralCompareUndefined(Expression** expr);
+  bool IsLiteralCompareUndefined(Expression** expr, Isolate* isolate);
   bool IsLiteralCompareNull(Expression** expr);
 
  protected: