Don't use `LinkedList` in the core libraries anymore.

sdk/lib/core/core.dart

 // 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.
 
 /**
  *
  * Built-in types, collections,
  * and other core functionality for every Dart program.
  *
  * This library is automatically imported.
@@ skipping 135 matching lines @@
  * More](https://www.dartlang.org/docs/dart-up-and-running/ch03.html#dartcore---numbers-collections-strings-and-more)
  * for more coverage of classes in this package.
  *
  * The
  * [Dart Language Specification](http://www.dartlang.org/docs/spec/)
  * provides technical details.
  */
 library dart.core;
 
 import "dart:collection";
-import "dart:_internal" hide Symbol;
+import "dart:_internal" hide Symbol, LinkedList, LinkedListEntry;
 import "dart:_internal" as internal show Symbol;
 import "dart:convert"
     show Encoding, ASCII, LATIN1, UTF8, BASE64, StringConversionSink;
 import "dart:math" show Random; // Used by List.shuffle.
 import "dart:typed_data" show Uint8List;
 
 part "annotations.dart";
 part "bool.dart";
 part "comparable.dart";
 part "date_time.dart";
@@ skipping 19 matching lines @@
 part "set.dart";
 part "sink.dart";
 part "stacktrace.dart";
 part "stopwatch.dart";
 part "string.dart";
 part "string_buffer.dart";
 part "string_sink.dart";
 part "symbol.dart";
 part "type.dart";
 part "uri.dart";