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

sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.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.
 
 library mirrors_dart2js;
 
 import 'dart:async';
 import 'dart:collection' show LinkedHashMap;
-import 'dart:uri';
 
 import '../../compiler.dart' as api;
 import '../elements/elements.dart';
 import '../apiimpl.dart' as apiimpl;
 import '../scanner/scannerlib.dart' hide SourceString;
 import '../dart2jslib.dart';
 import '../dart_types.dart';
 import '../source_file.dart';
 import '../tree/tree.dart';
 import '../util/util.dart' show Spannable, Link;
@@ skipping 1669 matching lines @@
  *
  * All API in this class is experimental.
  */
 class BackDoor {
   /// Return the compilation units comprising [library].
   static List<Mirror> compilationUnitsOf(Dart2JsLibraryMirror library) {
     return library._library.compilationUnits.toList().map(
         (cu) => new Dart2JsCompilationUnitMirror(cu, library)).toList();
   }
 }