[Intl] Fix Null-dereference in CreateICUDateFormatFromCache

Bug: chromium:930304
Change-Id: I7793f83b3f3e9aeaa3ecf114c6064773257e90e8
Reviewed-on: https://chromium-review.googlesource.com/c/1461167Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59587}

src/objects/js-date-time-format.cc

@@ -924,7 +924,10 @@ class DateFormatCache {
     if (map_.size() > 8) {  // Cache at most 8 DateFormats.
       map_.clear();
     }
-    map_[key] = CreateICUDateFormat(icu_locale, skeleton, generator);
+    std::unique_ptr<icu::SimpleDateFormat> instance(
+        CreateICUDateFormat(icu_locale, skeleton, generator));
+    if (instance.get() == nullptr) return nullptr;
+    map_[key] = std::move(instance);
     return static_cast<icu::SimpleDateFormat*>(map_[key]->clone());
   }
 

test/intl/regress-930304.js

+// Copyright 2019 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.
+
+assertDoesNotThrow(() => Intl.DateTimeFormat('en-u-nu-ethi'));