Add integration tests for the execution domain.

pkg/analysis_server/test/integration/execution/create_context_test.dart

+// 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 'package:test/test.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../integration_tests.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(CreateContextTest);
+  });
+}
+
+@reflectiveTest
+class CreateContextTest extends AbstractAnalysisServerIntegrationTest {
+  test_create() async {
+    standardAnalysisSetup();
+    String contextId =
+        (await sendExecutionCreateContext(sourceDirectory.path)).id;
+    expect(contextId, isNotNull);
+  }
+
+  @override
+  bool get enableNewAnalysisDriver => true;
+}