Add skyx packages for all the Sky demos (except game)

sky/tools/skyx/bin/skyx.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:io';
 import 'dart:async';
 
 import 'package:archive/archive.dart';
 import 'package:args/args.dart';
 import 'package:yaml/yaml.dart';
@@ skipping 47 matching lines @@
   if (manifestDescriptor == null || !manifestDescriptor.containsKey('material-design-icons'))
     return;
   for (Map assetDescriptor in manifestDescriptor['material-design-icons']) {
     for (MaterialAsset asset in generateMaterialAssets(assetDescriptor)) {
       yield asset;
     }
   }
 }
 
 Future loadManifest(String manifestPath) async {
+  if (manifestPath == null)
+    return null;
   String manifestDescriptor = await new File(manifestPath).readAsString();
   return loadYaml(manifestDescriptor);
 }
 
 Future<ArchiveFile> createFile(MaterialAsset asset, String assetBase) async {
   File file = new File('${assetBase}/${asset.key}');
   List<int> content = await file.readAsBytes();
   return new ArchiveFile.noCompress(asset.key, content.length, content);
 }
 
 Future<ArchiveFile> createSnapshotFile(String snapshotPath) async {
   File file = new File(snapshotPath);
   List<int> content = await file.readAsBytes();
   return new ArchiveFile(kSnapshotKey, content.length, content);
 }
 
 main(List<String> argv) async {
   ArgParser parser = new ArgParser();
   parser.addFlag('help', abbr: 'h', negatable: false);
   parser.addOption('asset-base');
+  parser.addOption('manifest');
+  parser.addOption('output-file', abbr: 'o');
   parser.addOption('snapshot');
-  parser.addOption('output-file', abbr: 'o');
 
   ArgResults args = parser.parse(argv);
   if (args['help']) {
     print(parser.usage);
     return;
   }
 
-  String manifestPath = args.rest.first;
-
+  String manifestPath = args['manifest'];
   Map manifestDescriptor = await loadManifest(manifestPath);
   Iterable<MaterialAsset> materialAssets = parseMaterialAssets(manifestDescriptor);
 
   Archive archive = new Archive();
 
   String snapshot = args['snapshot'];
   if (snapshot != null)
     archive.addFile(await createSnapshotFile(snapshot));
 
   for (MaterialAsset asset in materialAssets)
     archive.addFile(await createFile(asset, args['asset-base']));
 
   File outputFile = new File(args['output-file']);
   await outputFile.writeAsBytes(new ZipEncoder().encode(archive));
 }