Change the process API to be completely asynchronous.

tools/testing/dart/test_suite.dart

Index: tools/testing/dart/test_suite.dart
diff --git a/tools/testing/dart/test_suite.dart b/tools/testing/dart/test_suite.dart
index e47c05f82596981f7f7ebb9568e52f7e72bd445c..7c566549110cf00f6c9dbcade3b23dc03fae33cf 100644
--- a/tools/testing/dart/test_suite.dart
+++ b/tools/testing/dart/test_suite.dart
@@ -20,7 +20,7 @@ class CCTestListerIsolate extends Isolate {
 
   void main() {
     port.receive((String runnerPath, SendPort replyTo) {
-      var p = new Process(runnerPath, ["--list"]);
+      var p = new Process.start(runnerPath, ["--list"]);
       StringInputStream stdoutStream = new StringInputStream(p.stdout);
       List<String> tests = new List<String>();
       stdoutStream.lineHandler = () {
@@ -40,7 +40,6 @@ class CCTestListerIsolate extends Isolate {
         }
         replyTo.send("");
       };
-      p.start();
     });
   }
 }