Make some pkg tests less timing-dependent.

pkg/analysis_server/test/mocks.dart

Index: pkg/analysis_server/test/mocks.dart
diff --git a/pkg/analysis_server/test/mocks.dart b/pkg/analysis_server/test/mocks.dart
index 04d3d0ec1808880acac1f53e10f3407aa5e0d5cd..3d719e33b878a8f36a239361b514d0063e70be6f 100644
--- a/pkg/analysis_server/test/mocks.dart
+++ b/pkg/analysis_server/test/mocks.dart
@@ -249,9 +249,6 @@ class MockServerChannel implements ServerCommunicationChannel {
 
   Future<Response> waitForResponse(Request request) {
     String id = request.id;
-    pumpEventQueue().then((_) {
-      responseController.addError(new NoResponseException(request));
-    });
     return new Future<Response>(() =>
         responseController.stream.firstWhere((response) => response.id == id));
   }