Move tools to tool folder.

pkg/front_end/lib/src/fasta/util/bytes_sink.dart

Index: pkg/front_end/lib/src/fasta/util/bytes_sink.dart
diff --git a/pkg/front_end/lib/src/fasta/util/bytes_sink.dart b/pkg/front_end/lib/src/fasta/util/bytes_sink.dart
new file mode 100644
index 0000000000000000000000000000000000000000..d945e92467229eda7acfb18c699d963d8e9dc490
--- /dev/null
+++ b/pkg/front_end/lib/src/fasta/util/bytes_sink.dart
@@ -0,0 +1,18 @@
+// Copyright (c) 2017, 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.
+
+import 'dart:io' show BytesBuilder;
+
+// TODO(ahe): https://github.com/dart-lang/sdk/issues/28316
+class BytesSink implements Sink<List<int>> {
+  final BytesBuilder builder = new BytesBuilder();
+
+  void add(List<int> data) {
+    builder.add(data);
+  }
+
+  void close() {
+    // Nothing to do.
+  }
+}