Reload native extensions when starting from a snapshot.

samples/sample_extension/test/sample_extension_test.dart

 // Copyright (c) 2013, 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.
 //
 // Dart test program for testing native extensions.
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
 
@@ skipping 20 matching lines @@
       return join(buildDirectory, 'lib.target', 'libsample_extension.so');
     case 'macos':
       return join(buildDirectory, 'libsample_extension.dylib');
     case 'windows':
       return join(buildDirectory, 'sample_extension.dll');
     default:
       Expect.fail('Unknown operating system ${Platform.operatingSystem}');
   }
 }
 
-void main() {
+void main() async {
   String buildDirectory = dirname(Platform.executable);
   Directory tempDirectory =
       Directory.systemTemp.createTempSync('sample_extension_');
-  String testDirectory = tempDirectory.path;
-  String sourceDirectory = Platform.script.resolve('..').toFilePath();
+  try {
+    String testDirectory = tempDirectory.path;
+    String sourceDirectory = Platform.script.resolve('..').toFilePath();
 
-  // Copy sample_extension shared library, sample_extension dart files and
-  // sample_extension tests to the temporary test directory.
-  copyFileToDirectory(getNativeLibraryPath(buildDirectory), testDirectory)
-  .then((_) => Future.forEach(['sample_synchronous_extension.dart',
-                               'sample_asynchronous_extension.dart',
-                               'test_sample_synchronous_extension.dart',
-                               'test_sample_asynchronous_extension.dart'],
-    (file) => copyFileToDirectory(join(sourceDirectory, file), testDirectory)
-  ))
+    // Copy sample_extension shared library, sample_extension dart files and
+    // sample_extension tests to the temporary test directory.
+    await copyFileToDirectory(getNativeLibraryPath(buildDirectory),
+                              testDirectory);
+    for (var file in ['sample_synchronous_extension.dart',
+                      'sample_asynchronous_extension.dart',
+                      'test_sample_synchronous_extension.dart',
+                      'test_sample_asynchronous_extension.dart']) {
+      await copyFileToDirectory(join(sourceDirectory, file), testDirectory);
+    }
 
-  .then((_) => Future.forEach(['test_sample_synchronous_extension.dart',
-                               'test_sample_asynchronous_extension.dart'],
-    (test) => Process.run(Platform.executable, [join(testDirectory, test)])
-    .then((ProcessResult result) {
+    for (var test in ['test_sample_synchronous_extension.dart',
+                      'test_sample_asynchronous_extension.dart']) {
+      String script = join(testDirectory, test);
+      ProcessResult result = await Process.run(Platform.executable, [script]);
       if (result.exitCode != 0) {
         print('Failing test: ${join(sourceDirectory, test)}');
         print('Failing process stdout: ${result.stdout}');
         print('Failing process stderr: ${result.stderr}');
         print('End failing process stderr');
         Expect.fail('Test failed with exit code ${result.exitCode}');
       }
-    })
-  ))
-  .whenComplete(() => tempDirectory.deleteSync(recursive: true));
+    }
+  } finally {
+    await tempDirectory.deleteSync(recursive: true);
+  }
 }