Move flat_buffer and api_signature into front_end.

pkg/front_end/test/src/base/flat_buffers_test.dart

Index: pkg/front_end/test/src/base/flat_buffers_test.dart
diff --git a/pkg/analyzer/test/src/summary/flat_buffers_test.dart b/pkg/front_end/test/src/base/flat_buffers_test.dart
similarity index 99%
rename from pkg/analyzer/test/src/summary/flat_buffers_test.dart
rename to pkg/front_end/test/src/base/flat_buffers_test.dart
index 2498fca5370fafcb93bfd620f2cada308541947d..f94c7ed1805dcb62aa498232c6ac28bb55093e56 100644
--- a/pkg/analyzer/test/src/summary/flat_buffers_test.dart
+++ b/pkg/front_end/test/src/base/flat_buffers_test.dart
@@ -2,11 +2,9 @@
 // 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.
 
-library test.src.summary.flat_buffers_test;
-
 import 'dart:typed_data';
 
-import 'package:analyzer/src/summary/flat_buffers.dart';
+import 'package:front_end/src/base/flat_buffers.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';