Clean up warnings and hints

pkg/analyzer/lib/src/summary/pub_summary.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:async';
 import 'dart:collection';
-import 'dart:core' hide Resource;
+import 'dart:core';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/scanner/reader.dart';
 import 'package:analyzer/src/dart/scanner/scanner.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/parser.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ skipping 757 matching lines @@
   }
 
   /**
    * Check whether the given `package:` [uri] is listed in the package map.
    */
   bool isListed(String uri) {
     String package = PubSummaryManager.getPackageName(uri);
     return names.contains(package);
   }
 }