Add support for DateTimeFormat.formatToParts

src/js/i18n.js

Index: src/js/i18n.js
diff --git a/src/js/i18n.js b/src/js/i18n.js
index ffef1e8954c6d82e9d921eca41c3e95c81766a61..1aca01af56c81c929df9e9a8c3c6b35e95299438 100644
--- a/src/js/i18n.js
+++ b/src/js/i18n.js
@@ -1799,6 +1799,20 @@ function formatDate(formatter, dateValue) {
                              new GlobalDate(dateMs));
 }
 
+function formatDateToParts(formatter, dateValue) {
+  var dateMs;
+  if (IS_UNDEFINED(dateValue)) {
+    dateMs = %DateCurrentTime();
+  } else {
+    dateMs = TO_NUMBER(dateValue);
+  }
+
+  if (!NUMBER_IS_FINITE(dateMs)) throw %make_range_error(kDateRange);
+
+  return %InternalDateFormatToParts(
+      %GetImplFromInitializedIntlObject(formatter), new GlobalDate(dateMs));
+}
+
 
 /**
  * Returns a Date object representing the result of calling ToString(value)
@@ -1814,6 +1828,8 @@ function IntlParseDate(formatter, value) {
 
 // 0 because date is optional argument.
 AddBoundMethod(Intl.DateTimeFormat, 'format', formatDate, 0, 'dateformat');
+AddBoundMethod(Intl.DateTimeFormat, 'formatToParts', formatDateToParts, 0,
+               'dateformat');
 
 
 /**