Move Arrays class to private library.

tests/language/list_test.dart

Index: tests/language/list_test.dart
diff --git a/tests/language/list_test.dart b/tests/language/list_test.dart
index 1a9986f16364f2a558cd40a43c5fe494986fc56f..58000c72a2ab45a321957ea51ea0d9c8664ee6dd 100644
--- a/tests/language/list_test.dart
+++ b/tests/language/list_test.dart
@@ -57,6 +57,11 @@ class ListTest {
 
     Expect.throws(() {
       List a = new List(4);
+      a.setRange(1, 1, const [1, 2, 3, 4], null);
+    });
+
+    Expect.throws(() {
+      List a = new List(4);
       a.setRange(10, 1, a, 1);
     }, (e) => e is RangeError);