[regexp] Stage the dotall flag

test/mjsunit/harmony/regexp-dotall-disabled.js

Index: test/mjsunit/harmony/regexp-dotall-disabled.js
diff --git a/test/mjsunit/harmony/regexp-dotall-disabled.js b/test/mjsunit/harmony/regexp-dotall-disabled.js
index 79429c8c7e51e0db3a8a3035ef9da185faccbfce..825d3842dc7daba3331511277eb1e20aec90617d 100644
--- a/test/mjsunit/harmony/regexp-dotall-disabled.js
+++ b/test/mjsunit/harmony/regexp-dotall-disabled.js
@@ -5,6 +5,8 @@
 // This tests that RegExp dotall features are not enabled when
 // --harmony-regexp-dotall is not passed.
 
+// Flags: --no-harmony-regexp-dotall
+
 // Construction does not throw.
 {
   assertThrows("/./s", SyntaxError);