Merge the dart:uri library into dart:core and update the Uri class

utils/apidoc/apidoc.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.
 
 /**
  * This generates the reference documentation for the core libraries that come
  * with dart. It is built on top of dartdoc, which is a general-purpose library
  * for generating docs from any Dart code. This library extends that to include
  * additional information and styling specific to our standard library.
  *
  * Usage:
  *
  *     $ dart apidoc.dart [--out=<output directory>]
  */
 library apidoc;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:json' as json;
-import 'dart:uri';
 
 import 'html_diff.dart';
 
 // TODO(rnystrom): Use "package:" URL (#4968).
 import '../../sdk/lib/_internal/compiler/implementation/mirrors/mirrors.dart';
 import '../../sdk/lib/_internal/compiler/implementation/mirrors/mirrors_util.dart';
 import '../../sdk/lib/_internal/compiler/implementation/filenames.dart';
 import '../../sdk/lib/_internal/dartdoc/lib/dartdoc.dart';
 import '../../sdk/lib/_internal/libraries.dart';
 import 'package:pathos/path.dart' as pathos;
@@ skipping 454 matching lines @@
 /** Converts a local path string to a `file:` [Uri]. */
 Uri _pathToFileUri(String path) {
   path = pathos.absolute(path);
   if (Platform.operatingSystem != 'windows') {
     return Uri.parse('file://$path');
   } else {
     return Uri.parse('file:///${path.replaceAll("\\", "/")}');
   }
 }