[regexp] quantifier refers to the surrogate pair in unicode regexp.

test/cctest/test-regexp.cc

Index: test/cctest/test-regexp.cc
diff --git a/test/cctest/test-regexp.cc b/test/cctest/test-regexp.cc
index acbb26f7c7401ce42bb8c1dc6a0278c51cec0a6d..34e82a3deb5baf5538f891c529d6fcfdfc207956 100644
--- a/test/cctest/test-regexp.cc
+++ b/test/cctest/test-regexp.cc
@@ -312,6 +312,8 @@ void TestRegExpParser(bool lookbehind) {
   CheckParseEq("\\u{12345}\\u{23456}", "'\\ud808\\udf45\\ud84d\\udc56'", true);
   CheckParseEq("\\u{12345}|\\u{23456}", "(| '\\ud808\\udf45' '\\ud84d\\udc56')",
                true);
+  CheckParseEq("\u{12345}{3}", "(# 3 3 g '\ud808\udf45')", true);
+  CheckParseEq("\u{12345}*", "(# 0 - g '\ud808\udf45')", true);
 
   CHECK_SIMPLE("", false);
   CHECK_SIMPLE("a", true);