Clean up warnings and hints

pkg/analyzer_cli/lib/src/build_mode.dart

 // Copyright (c) 2015, 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 analyzer_cli.src.build_mode;
 
-import 'dart:core' hide Resource;
+import 'dart:core';
 import 'dart:io' as io;
 
 import 'package:analyzer/dart/ast/ast.dart' show CompilationUnit;
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/sdk/sdk.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ skipping 419 matching lines @@
    * Build the inverse mapping of [uriToSourceMap].
    */
   static Map<String, Uri> _computePathToUriMap(Map<Uri, File> uriToSourceMap) {
     Map<String, Uri> pathToUriMap = <String, Uri>{};
     uriToSourceMap.forEach((Uri uri, File file) {
       pathToUriMap[file.path] = uri;
     });
     return pathToUriMap;
   }
 }