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

tests/compiler/dart2js/dart_backend_test.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.
 
 import "package:expect/expect.dart";
 import 'dart:async';
-import 'dart:uri';
 import 'parser_helper.dart';
 import 'mock_compiler.dart';
 import '../../../sdk/lib/_internal/compiler/compiler.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart' as leg;
 import '../../../sdk/lib/_internal/compiler/implementation/dart_backend/dart_backend.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/elements/elements.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/tree/tree.dart';
 
 const coreLib = r'''
 library corelib;
@@ skipping 63 matching lines @@
       stripTypes: stripTypes);
 }
 
 /**
  * Library name is assumed to be 'mylib' in 'mylib.dart' file.
  */
 testDart2DartWithLibrary(
     String srcMain, String srcLibrary,
     {void continuation(String s), bool minify: false,
     bool stripTypes: false}) {
-  fileUri(path) => new Uri.fromComponents(scheme: 'file', path: path);
+  fileUri(path) => new Uri(scheme: 'file', path: path);
 
   final scriptUri = fileUri('script.dart');
   final libUri = fileUri('mylib.dart');
 
   provider(uri) {
     if (uri == scriptUri) return new Future.value(srcMain);
     if (uri.toString() == libUri.toString()) {
       return new Future.value(srcLibrary);
     }
     if (uri.path.endsWith('/core.dart')) {
@@ skipping 621 matching lines @@
   testStaticAccessIoLib();
   testLocalFunctionPlaceholder();
   testMinification();
   testClosureLocalsMinified();
   testParametersMinified();
   testDeclarationTypePlaceholders();
   testPlatformLibraryMemberNamesAreFixed();
   testConflictsWithCoreLib();
   testUnresolvedNamedConstructor();
 }