Eliminate dependencies on pkg/front_end.

pkg/analyzer/lib/src/dart/analysis/file_byte_store.dart

Index: pkg/analyzer/lib/src/dart/analysis/file_byte_store.dart
diff --git a/pkg/analyzer/lib/src/dart/analysis/file_byte_store.dart b/pkg/analyzer/lib/src/dart/analysis/file_byte_store.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c17428c000f83c1af757a252f360a79a5a9eb344
--- /dev/null
+++ b/pkg/analyzer/lib/src/dart/analysis/file_byte_store.dart
@@ -0,0 +1,9 @@
+// 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.
+
+// This library re-exports the parts of front_end's file_byte_store.dart whose
+// API is stable enough to be relied upon by clients.
+
+export 'package:front_end/src/incremental/file_byte_store.dart'
+    show FileByteStore;