Roll Observatory packages and add a roll script

packages/analyzer/test/src/context/test_all.dart

+// Copyright (c) 2015, 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.
+
+library test.src.context.test_all;
+
+import 'package:unittest/unittest.dart';
+
+import '../../utils.dart';
+import 'cache_test.dart' as cache_test;
+import 'context_test.dart' as context_test;
+
+/// Utility for manually running all tests.
+main() {
+  initializeTestEnvironment();
+  group('context tests', () {
+    cache_test.main();
+    context_test.main();
+  });
+}