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>[];
-
-  Library getLibraryReference(Uri uri) {
-    assert(uri.hasScheme);
-    return _uriToLibrary.putIfAbsent(uri, () => _buildLibraryReference(uri));
-  }
-
-  Library _buildLibraryReference(Uri uri) {
-    assert(uri.hasScheme);
-    var library = new Library(uri, isExternal: true)..fileUri = '$uri';
-    libraries.add(library);
-    return library;
-  }
-}