add dart:isolate import to bootstrap code, prepare for release (#600)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a0d2ad1..7b68ca0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.12.20+11
+
+* Refactor bootstrapping to simplify the test/pub_serve transformer.
+
 ## 0.12.20+10
 
 * Refactor for internal tools.
diff --git a/lib/pub_serve.dart b/lib/pub_serve.dart
index c403bfb..eacccf2 100644
--- a/lib/pub_serve.dart
+++ b/lib/pub_serve.dart
@@ -30,6 +30,8 @@
     transform.addOutput(new Asset.fromString(
         id.addExtension('.vm_test.dart'),
         '''
+          import "dart:isolate";
+
           import "package:test/bootstrap/vm.dart";
 
           import "${p.url.basename(id.path)}" as test;
diff --git a/pubspec.yaml b/pubspec.yaml
index 1afc8da..cdc8e7b 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: test
-version: 0.12.20+10
+version: 0.12.20+11
 author: Dart Team <misc@dartlang.org>
 description: A library for writing dart unit tests.
 homepage: https://github.com/dart-lang/test