Add in-process http server to the dart test scripts.

tools/testing/dart/test_progress.dart

Index: tools/testing/dart/test_progress.dart
diff --git a/tools/testing/dart/test_progress.dart b/tools/testing/dart/test_progress.dart
index 5343ac0d363e02e6e8664057cf2676980aa1d4bd..1f1f55702609dbaac0b231f361c002e50877f91a 100644
--- a/tools/testing/dart/test_progress.dart
+++ b/tools/testing/dart/test_progress.dart
@@ -220,7 +220,7 @@ class SilentProgressIndicator extends ProgressIndicator {
   }
 }
 
-class CompactIndicator extends ProgressIndicator {
+abstract class CompactIndicator extends ProgressIndicator {
   CompactIndicator(Date startTime, bool printTiming)
       : super(startTime, printTiming);
 
@@ -250,7 +250,7 @@ class CompactIndicator extends ProgressIndicator {
   void _printStartProgress(TestCase test) => _printProgress();
   void _printDoneProgress(TestCase test) => _printProgress();
 
-  abstract void _printProgress();
+  void _printProgress();
 }