Better codegen for '<expression> === void <literal>'.

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index fb1643e0c4e744a24b355ee4ffc08076479f49e6..045404a49db3fa5029d0a142d7d4d826c639c19f 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -1473,6 +1473,10 @@ class CompareOperation: public Expression {
   bool IsSmiCompare() { return compare_type_ == SMI_ONLY; }
   bool IsObjectCompare() { return compare_type_ == OBJECT_ONLY; }
 
+  // Match special cases.
+  bool IsLiteralCompareTypeof(Expression** expr, Handle<String>* check);
+  bool IsLiteralCompareUndefined(Expression** expr);
+
  private:
   Token::Value op_;
   Expression* left_;