Remove dart2js specific core.dart and coreimpl.dart files.

lib/compiler/implementation/lib/mock.dart

Index: lib/compiler/implementation/lib/mock.dart
diff --git a/lib/compiler/implementation/lib/mock.dart b/lib/compiler/implementation/lib/mock.dart
deleted file mode 100644
index ef49c989286310f620930dea49efb8f315a74753..0000000000000000000000000000000000000000
--- a/lib/compiler/implementation/lib/mock.dart
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright (c) 2012, 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.
-
-// Mocks of things that Leg cannot read directly.
-
-// TODO(ahe): Remove this file.
-
-// TODO(ahe): Not sure ByteArray belongs in the core library.
-interface Uint8List extends List default _InternalByteArray {
-  Uint8List(int length);
-}
-
-class _InternalByteArray {
-  factory Uint8List(int length) {
-    throw new UnsupportedOperationException("new Uint8List($length)");
-  }
-}