include exported library namespace in prefixed import suggestions

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

Index: pkg/analysis_server/lib/src/services/completion/suggestion_builder.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/suggestion_builder.dart b/pkg/analysis_server/lib/src/services/completion/suggestion_builder.dart
index 157a9e0808063496454268dbdc9303710d13e7bb..e1132b537a53b83b54f8cae26f2534f80fd3e1fd 100644
--- a/pkg/analysis_server/lib/src/services/completion/suggestion_builder.dart
+++ b/pkg/analysis_server/lib/src/services/completion/suggestion_builder.dart
@@ -476,6 +476,12 @@ class LibraryElementSuggestionBuilder extends GeneralizingElementVisitor
   @override
   visitCompilationUnitElement(CompilationUnitElement element) {
     element.visitChildren(this);
+    LibraryElement containingLibrary = element.library;
+    if (containingLibrary != null) {
+      for (var lib in containingLibrary.exportedLibraries) {
+        lib.visitChildren(this);
+      }
+    }
   }
 
   @override