Revert "Package map source factory support" [TBR].

pkg/analyzer/lib/src/generated/source_io.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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.source.io;
 
 import 'dart:collection';
@@ skipping 265 matching lines @@
   static String FILE_SCHEME = "file";
 
   @override
   Source resolveAbsolute(Uri uri) {
     if (!isFileUri(uri)) {
       return null;
     }
     return new FileBasedSource(new JavaFile.fromUri(uri), uri);
   }
 
-  @override
-  Uri restoreAbsolute(Source source) {
-    if (source is FileBasedSource) {
-      return new Uri.file(source.file.getAbsolutePath());
-    }
-    return null;
-  }
   /**
    * Return `true` if the given URI is a `file` URI.
    *
    * @param uri the URI being tested
    * @return `true` if the given URI is a `file` URI
    */
   static bool isFileUri(Uri uri) => uri.scheme == FILE_SCHEME;
 }
 
 /**
@@ skipping 249 matching lines @@
   }
 
   /**
    * Return `true` if the given URI is a `file` URI.
    *
    * @param uri the URI being tested
    * @return `true` if the given URI is a `file` URI
    */
   static bool isFileUri(Uri uri) => uri.scheme == FILE_SCHEME;
 }