include unimported sdk lib types as low priority suggestions

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

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library services.completion.dart.cache;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analysis_server/src/protocol_server.dart'
@@ skipping 259 matching lines @@
       _importedCompletions.add(suggestion.completion);
     }
   }
 
   /**
    * Add suggestions for all top level elements in the context
    * excluding those elemnents for which suggestions have already been added.
    */
   void _addNonImportedElementSuggestions(
       List<SearchMatch> matches, Set<LibraryElement> excludedLibs) {
+    AnalysisContext sdkContext = context.sourceFactory.dartSdk.context;
     matches.forEach((SearchMatch match) {
       if (match.kind == MatchKind.DECLARATION) {
         Element element = match.element;
-        if (element.context == context &&
+        if ((element.context == context || element.context == sdkContext) &&
             element.isPublic &&
             !excludedLibs.contains(element.library) &&
             !_importedCompletions.contains(element.displayName)) {
           _addSuggestion(element, DART_RELEVANCE_LOW);
         }
       }
     });
   }
 
   /**
@@ skipping 89 matching lines @@
   @override
   void visitFunctionTypeAliasElement(FunctionTypeAliasElement element) {
     cache._addSuggestion(element, DART_RELEVANCE_DEFAULT);
   }
 
   @override
   void visitTopLevelVariableElement(TopLevelVariableElement element) {
     cache._addSuggestion(element, DART_RELEVANCE_DEFAULT);
   }
 }