Run test tearDowns and clean up temporary directories when a signal is caught.

test/runner/browser/compact_reporter_test.dart

Index: test/runner/browser/compact_reporter_test.dart
diff --git a/test/runner/browser/compact_reporter_test.dart b/test/runner/browser/compact_reporter_test.dart
index 24045229d8b888f1d3146c6c7be51d7e9fb4e02f..94b748d2aa7019fc23d58c7735db3648c859dd9b 100644
--- a/test/runner/browser/compact_reporter_test.dart
+++ b/test/runner/browser/compact_reporter_test.dart
@@ -7,6 +7,7 @@
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
+import 'package:test/src/util/io.dart';
 import 'package:test/test.dart';
 
 import '../../io.dart';
@@ -15,7 +16,7 @@ String _sandbox;
 
 void main() {
   setUp(() {
-    _sandbox = Directory.systemTemp.createTempSync('test_').path;
+    _sandbox = createTempDir();
   });
 
   tearDown(() {