Make 'where' lazy.

pkg/intl/test/date_time_format_test_core.dart

Index: pkg/intl/test/date_time_format_test_core.dart
diff --git a/pkg/intl/test/date_time_format_test_core.dart b/pkg/intl/test/date_time_format_test_core.dart
index 4e92fb648235c887c84b19525702086080e52a50..9ba522c1d2c357e6b8aa28fe7470c910d819064c 100644
--- a/pkg/intl/test/date_time_format_test_core.dart
+++ b/pkg/intl/test/date_time_format_test_core.dart
@@ -177,7 +177,7 @@ List<String> allLocales() => DateFormat.allLocalesWithSymbols();
  */
 List oddLocales() {
   int i = 1;
-  return allLocales().where((x) => (i++).isOdd);
+  return allLocales().where((x) => (i++).isOdd).toList();
 }
 
 /**
@@ -193,7 +193,7 @@ List smallSetOfLocales() {
  */
 List evenLocales() {
   int i = 1;
-  return allLocales().where((x) => !((i++).isOdd));
+  return allLocales().where((x) => !((i++).isOdd)).toList();
 }
 
 // TODO(alanknight): Run specific tests for the en_ISO locale which isn't