add dart: and package: import uri suggestions

pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart

Index: pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart b/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
index c1b033917509bfc4a622369b4c03edc8c951315a..bb7d55c656364332fd23e9dcc21d37d16e967881 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
@@ -13,11 +13,12 @@ import 'package:analysis_server/src/services/completion/common_usage_computer.da
 import 'package:analysis_server/src/services/completion/completion_manager.dart';
 import 'package:analysis_server/src/services/completion/completion_target.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_cache.dart';
+import 'package:analysis_server/src/services/completion/import_uri_contributor.dart';
 import 'package:analysis_server/src/services/completion/imported_reference_contributor.dart';
-import 'package:analysis_server/src/services/completion/prefixed_element_contributor.dart';
 import 'package:analysis_server/src/services/completion/keyword_contributor.dart';
 import 'package:analysis_server/src/services/completion/local_reference_contributor.dart';
 import 'package:analysis_server/src/services/completion/optype.dart';
+import 'package:analysis_server/src/services/completion/prefixed_element_contributor.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
@@ -86,7 +87,8 @@ class DartCompletionManager extends CompletionManager {
         new KeywordContributor(),
         new ArgListContributor(),
         new CombinatorContributor(),
-        new PrefixedElementContributor()
+        new PrefixedElementContributor(),
+        new ImportUriContributor(),
       ];
     }
     if (commonUsageComputer == null) {