Add an Environment class that's exposed through RunnerSuite.

lib/src/runner/loader.dart

Index: lib/src/runner/loader.dart
diff --git a/lib/src/runner/loader.dart b/lib/src/runner/loader.dart
index 0b6c83815caca7dab9e904feb4b8fbaabec9228e..964809e73131e6e8814e6c0c8797254d6306e724 100644
--- a/lib/src/runner/loader.dart
+++ b/lib/src/runner/loader.dart
@@ -25,6 +25,7 @@ import 'load_exception.dart';
 import 'load_suite.dart';
 import 'parse_metadata.dart';
 import 'runner_suite.dart';
+import 'vm/environment.dart';
 import 'vm/isolate_test.dart';
 
 /// A class for finding test files and loading them into a runnable form.
@@ -159,7 +160,7 @@ class Loader {
 
       // Don't load a skipped suite.
       if (metadata.skip) {
-        yield new LoadSuite.forSuite(new RunnerSuite([
+        yield new LoadSuite.forSuite(new RunnerSuite(const VMEnvironment(), [
           new LocalTest(path, metadata, () {})
         ], path: path, platform: platform, metadata: metadata));
         continue;
@@ -262,7 +263,8 @@ void main(_, Map message) {
     });
 
     try {
-      var suite = new RunnerSuite((await completer.future).map((test) {
+      var suite = new RunnerSuite(const VMEnvironment(),

[kevmoo, 2015/07/30 01:37:24]

nested awaits worry me – could make debugging that much more difficult. Pop out
if you think it's okay.

[nweiz, 2015/07/30 19:41:50]

Part of the point of await is that it can be used in subexpressions. I don't
think that makes it any harder to debug than any other subexpression.

+          (await completer.future).map((test) {
         var testMetadata = new Metadata.deserialize(test['metadata']);
         return new IsolateTest(test['name'], testMetadata, test['sendPort']);
       }),