Add ServerOperation and queue.

pkg/analysis_server/test/domain_analysis_test.dart

Index: pkg/analysis_server/test/domain_analysis_test.dart
diff --git a/pkg/analysis_server/test/domain_analysis_test.dart b/pkg/analysis_server/test/domain_analysis_test.dart
index fc429e37cf8d377f73e77058fe073d6dfbf2b595..2c9153e085844c3b7e3785ec0bbcb875b2f4ab56 100644
--- a/pkg/analysis_server/test/domain_analysis_test.dart
+++ b/pkg/analysis_server/test/domain_analysis_test.dart
@@ -262,7 +262,7 @@ class AnalysisTestHelper {
   }
 
   /**
-   * Creates an empty project `/project/`.
+   * Creates an empty project `/project`.
    */
   void createEmptyProject() {
     resourceProvider.newFolder('/project');
@@ -1104,7 +1104,7 @@ testUpdateContent() {
         helper.handleSuccessfulRequest(request);
       }
       // wait, there is an error
-      helper.waitForTasksFinished().then((_) {
+      return helper.waitForTasksFinished().then((_) {
         List<AnalysisError> errors = helper.getTestErrors();
         expect(errors, hasLength(1));
       });
@@ -1133,7 +1133,7 @@ testUpdateContent() {
         helper.handleSuccessfulRequest(request);
       }
       // wait, there is an error
-      helper.waitForTasksFinished().then((_) {
+      return helper.waitForTasksFinished().then((_) {
         List<AnalysisError> errors = helper.getTestErrors();
         expect(errors, hasLength(1));
       });