Block scoped const variables.

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index 2ae1364d32d98df66b93b0b0fd81e71a0099e151..3bb4eb541eec8cd5b26447920639a3786268b727 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -405,7 +405,10 @@ class Declaration: public AstNode {
         mode_(mode),
         fun_(fun),
         scope_(scope) {
-    ASSERT(mode == VAR || mode == CONST || mode == LET);
+    ASSERT(mode == VAR ||
+           mode == CONST ||
+           mode == CONST_HARMONY ||
+           mode == LET);
     // At the moment there are no "const functions"'s in JavaScript...
     ASSERT(fun == NULL || mode == VAR || mode == LET);
   }