fix CombinatorContributor to only suggest public members

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

Index: pkg/analysis_server/lib/src/services/completion/dart/combinator_contributor.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/combinator_contributor.dart b/pkg/analysis_server/lib/src/services/completion/dart/combinator_contributor.dart
index a08b8bb30c0fa66fc2079aea8c7f1ee73546f27d..d7bf1ea2b4cba0e1e1994770b1d1e42a1472be54 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart/combinator_contributor.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart/combinator_contributor.dart
@@ -32,8 +32,8 @@ class CombinatorContributor extends DartCompletionContributor {
       LibraryElement library = directive.uriElement;
       if (library != null) {
         LibraryElementSuggestionBuilder builder =
-            new LibraryElementSuggestionBuilder(
-                library, CompletionSuggestionKind.IDENTIFIER, false, false);
+            new LibraryElementSuggestionBuilder(request.libraryElement,
+                CompletionSuggestionKind.IDENTIFIER, false, false);
         library.visitChildren(builder);
         return builder.suggestions;
       }