Fix format of -NAN in toLocaleString()

Bug: chromium:1030160
Change-Id: I4e1b762b10c77ec671712355c61cdbb0b5f033da
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2068725Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66411}

src/objects/js-number-format.cc

@@ -1252,7 +1252,9 @@ Maybe<icu::UnicodeString> IcuFormatNumber(
     formatted = number_format.formatDecimal(
         {big_int_string->ToCString().get(), big_int_string->length()}, status);
   } else {
-    double number = numeric_obj->Number();
+    double number = numeric_obj->IsNaN()
+                        ? std::numeric_limits<double>::quiet_NaN()
+                        : numeric_obj->Number();
     formatted = number_format.formatDouble(number, status);
   }
   if (U_FAILURE(status)) {

test/intl/regress-1030160.js

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+assertEquals("NaN", (null/null).toLocaleString());