Add a platform plugin infrastructure.

lib/src/runner/hack_load_vm_file_hook.dart

Index: lib/src/runner/hack_load_vm_file_hook.dart
diff --git a/lib/src/runner/hack_load_vm_file_hook.dart b/lib/src/runner/hack_load_vm_file_hook.dart
deleted file mode 100644
index c921d9a53a7168a8c3c77aa1a05074203cc4d3da..0000000000000000000000000000000000000000
--- a/lib/src/runner/hack_load_vm_file_hook.dart
+++ /dev/null
@@ -1,21 +0,0 @@
-// 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.
-
-import 'dart:async';
-
-import '../backend/metadata.dart';
-import 'configuration.dart';
-import 'runner_suite.dart';
-
-typedef Future<RunnerSuite> LoadVMFileHook(String path, Metadata metadata,
-    Configuration config);
-
-/// **Do not set or use this function without express permission from the test
-/// package authors**.
-///
-/// A function that overrides the loader's default behavior for loading test
-/// suites on the Dart VM. This function takes the path to the file, the
-/// file's metadata, and the test runner's configuration and returns a
-/// [RunnerSuite] for that file.
-LoadVMFileHook loadVMFileHook;