Rationalize Dart mojo and sky package structure

mojo/dart/embedder/builtin.dart

 // Copyright 2014 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.
 
 library mojo_builtin;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:mojo.internal';
 
@@ skipping 45 matching lines @@
 void _setWorkingDirectory(cwd) {
   cwd = _enforceTrailingSlash(cwd);
   _workingDirectoryUri = new Uri(scheme: 'file', path: cwd);
   if (_logBuiltin) {
     _print('# Working Directory: $cwd');
   }
 }
 
 _setPackageRoot(String packageRoot) {
   packageRoot = _enforceTrailingSlash(packageRoot);
+
   if (packageRoot.startsWith('file:') ||
       packageRoot.startsWith('http:') ||
       packageRoot.startsWith('https:')) {
     _packageRoot = _workingDirectoryUri.resolve(packageRoot);
   } else {
     _packageRoot = _workingDirectoryUri.resolveUri(new Uri.file(packageRoot));
   }
   if (_logBuiltin) {
     _print('# Package root: $packageRoot -> $_packageRoot');
   }
@@ skipping 148 matching lines @@
     //   _loadScript(tag, uri, libraryUri, data);
     // });
     throw 'Cannot load http, yet.';
   } else {
     // Mojo does not expose any asynchronous file IO calls, but we'll maintain
     // the same structure as the standalone embedder here in case it ever does.
     var data = readSync(resourceUri.toFilePath());
     _loadScript(tag, uri, libraryUri, data);
   }
 }