Move SplayTreeMap from coreimpl to collection.

tests/language/import_core_impl_no_prefix_test.dart

Index: tests/language/import_core_impl_no_prefix_test.dart
diff --git a/tests/language/import_core_impl_no_prefix_test.dart b/tests/language/import_core_impl_no_prefix_test.dart
deleted file mode 100644
index 434d6067a05e5ef02b18aa85ca049f3fa64cf591..0000000000000000000000000000000000000000
--- a/tests/language/import_core_impl_no_prefix_test.dart
+++ /dev/null
@@ -1,13 +0,0 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-// Dart test program importing the core library explicitly.
-
-#library("ImportCoreImplNoPrefixTest.dart");
-#import("dart:coreimpl");
-
-main() {
-  var e = new SplayTreeMap();
-  print('"dart:coreimpl" imported, $e allocated');
-}