Make the date_time_format_http_request_test run faster

pkg/intl/test/date_time_format_test_core.dart

Index: pkg/intl/test/date_time_format_test_core.dart
===================================================================
--- pkg/intl/test/date_time_format_test_core.dart	(revision 13132)
+++ pkg/intl/test/date_time_format_test_core.dart	(working copy)
@@ -182,6 +182,13 @@
 }
 
 /**
+ * Return a set of a few locales to run just the tests on a small sample.
+ */
+List smallSetOfLocales() {
+  return allLocales().getRange(0,10);
+}
+
+/**
  * Return only the even-numbered locales. A simple way to divide the list into
  * two roughly equal parts.
  */