Fix mirror usage in pub test.

sdk/lib/_internal/pub/lib/src/utils.dart

 // Copyright (c) 2012, 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.
 
 /// Generic utility functions. Stuff that should possibly be in core.
 library utils;
 
 import 'dart:async';
 import 'dart:crypto';
 import 'dart:io';
@@ skipping 345 matching lines @@
     var map = {};
     for (var pair in resolvedPairs) {
       map[pair.first] = pair.last;
     }
     return map;
   });
 }
 
 /// Returns the path to the library named [libraryName]. The library name must
 /// be globally unique, or the wrong library path may be returned.
-String libraryPath(String libraryName) =>
-  fileUriToPath(currentMirrorSystem().libraries[new Symbol(libraryName)].uri);
+String libraryPath(String libraryName) {
+  var libraries = currentMirrorSystem().findLibrary(new Symbol(libraryName));
+  return fileUriToPath(libraries.single.uri);
+}
 
 /// Converts a `file:` [Uri] to a local path string.
 String fileUriToPath(Uri uri) {
   if (uri.scheme != 'file') {
     throw new ArgumentError("Uri $uri must have scheme 'file:'.");
   }
   if (Platform.operatingSystem != 'windows') return uri.path;
   if (uri.path.startsWith("/")) {
     // Drive-letter paths look like "file:///C:/path/to/file". The replaceFirst
     // removes the extra initial slash.
@@ skipping 27 matching lines @@
     error is FileIOException ||
     error is HttpException ||
     error is HttpParserException ||
     error is LinkIOException ||
     error is MimeParserException ||
     error is OSError ||
     error is ProcessException ||
     error is SocketIOException ||
     error is WebSocketException;
 }