When only listing and not running tests, don't start the http server.

tools/test.dart

Index: tools/test.dart
diff --git a/tools/test.dart b/tools/test.dart
index 22aca2c2de6d14af23612bf23e5effd1a7e6771f..f7115aab2237ad69b5b48442a0b0cec76284c29e 100755
--- a/tools/test.dart
+++ b/tools/test.dart
@@ -127,7 +127,7 @@ main() {
   // Start global http server that serves the entire dart repo.
   // The http server is available on localhost:9876 for any
   // test that needs to load resources from the repo over http.
-  startHttpServer('127.0.0.1', 9876);
+  if (!listTests) startHttpServer('127.0.0.1', 9876);
 
   // Start process queue.
   new ProcessQueue(
@@ -136,7 +136,9 @@ main() {
       startTime,
       printTiming,
       enqueueConfiguration,
-      () => terminateHttpServer(),
+      () {
+        if (!listTests) terminateHttpServer();
+      },
       verbose,
       listTests);
 }