create new Dart specific completion contributor extension point

pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart

Index: pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart
diff --git a/pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart b/pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart
index 91ebc1b92c37ebb092bb6b8fc268c03c7bc171cb..f6f1f463b2765888c56d3f6b38133a9e3a0eb993 100644
--- a/pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart
+++ b/pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart
@@ -11,7 +11,8 @@ import 'package:analysis_server/plugin/protocol/protocol.dart' as protocol
 import 'package:analysis_server/plugin/protocol/protocol.dart'
     hide Element, ElementKind;
 import 'package:analysis_server/plugin/protocol/protocol.dart';
-import 'package:analysis_server/src/provisional/completion/completion_dart.dart';
+import 'package:analysis_server/src/analysis_server.dart';
+import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
 import 'package:analysis_server/src/services/completion/completion_core.dart';
 import 'package:analysis_server/src/services/completion/dart/completion_manager.dart'
     show DartCompletionRequestImpl;
@@ -24,6 +25,7 @@ import 'package:analyzer/src/generated/source.dart';
 import 'package:unittest/unittest.dart';
 
 import '../../../abstract_context.dart';
+import '../../../operation/operation_queue_test.dart';
 
 int suggestionComparator(CompletionSuggestion s1, CompletionSuggestion s2) {
   String c1 = s1.completion.toLowerCase();
@@ -131,8 +133,10 @@ abstract class DartCompletionContributorTest extends AbstractContextTest {
   }
 
   Future computeSuggestions([int times = 200]) async {
+    AnalysisServer server = new AnalysisServerMock(
+        searchEngine: searchEngine, resourceProvider: provider);
     CompletionRequestImpl baseRequest = new CompletionRequestImpl(
-        context, provider, testSource, completionOffset);
+        server, context, provider, testSource, completionOffset);
     request = new DartCompletionRequestImpl.forRequest(baseRequest);
     Completer<List<CompletionSuggestion>> completer =
         new Completer<List<CompletionSuggestion>>();