Implement canonical name scheme in kernel.

pkg/kernel/lib/repository.dart

 // Copyright (c) 2016, 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 kernel.repository;
 
 import 'ast.dart';
 
 /// Keeps track of which [Library] objects have been created for a given URI.
 ///
 /// To load different files into the same IR, pass in the same repository
 /// object to the loaders.
 class Repository {
-  final Map<Uri, Library> _uriToLibrary = <Uri, Library>{};
-  final List<Library> libraries = <Library>[];
+  final Program program = new Program();
 
-  Library getLibraryReference(Uri uri) {
-    assert(uri.hasScheme);
-    return _uriToLibrary.putIfAbsent(uri, () => _buildLibraryReference(uri));
-  }
+  Library getLibraryReference(Uri uri) => program.getLibraryReference(uri);
 
-  Library _buildLibraryReference(Uri uri) {
-    assert(uri.hasScheme);
-    var library = new Library(uri, isExternal: true)..fileUri = '$uri';
-    libraries.add(library);
-    return library;
-  }
+  List<Library> get libraries => program.libraries;
+  CanonicalName get root => program.root;
 }