Replace dart_core.js with actual compiled SDK

lib/src/utils.dart

 // Copyright (c) 2015, 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.
 
 /// Holds a couple utility functions used at various places in the system.
 library dev_compiler.src.utils;
 
 import 'dart:io';
 
 import 'package:path/path.dart' as path;
@@ skipping 300 matching lines @@
   if (resourceUri.scheme != 'file') return null;
   var filepath = resourceUri.path;
   var relativePath = path.relative(filepath, from: path.dirname(entryUri.path));
 
   // File:/// urls can be for resources in the same project or resources from
   // the dev_compiler package. For now we only support relative paths going
   // further inside the folder where the entrypoint is located, otherwise we
   // assume this is a runtime resource from the dev_compiler.
   if (!relativePath.startsWith('..')) return relativePath;
 
-  // Expect the code to live under lib/runtime/ in the dev_compiler's folder.
-  var filename = path.basename(filepath);
-  var dir = path.dirname(filepath);
-  if (path.basename(dir) != 'runtime') return null;
-  dir = path.dirname(dir);
-  if (path.basename(dir) != 'lib') return null;
-  dir = path.dirname(dir);
+  // Since this is a URI path we can assume forward slash and use lastIndexOf.
+  var runtimePath = '/lib/runtime/';
+  var pos = filepath.lastIndexOf(runtimePath);
+  if (pos == -1) return null;
+
+  var filename = filepath.substring(pos + runtimePath.length);
+  var dir = filepath.substring(0, pos);
+
+  // TODO(jmesserly): can we implement this without repeatedly reading pubspec?
+  // It seems like we should know our package's root directory without needing
+  // to search like this.
   var pubspec =
       loadYaml(new File(path.join(dir, 'pubspec.yaml')).readAsStringSync());
 
   // Ensure this is loaded from the dev_compiler package.
   if (pubspec['name'] != 'dev_compiler') return null;
   return path.join('dev_compiler', 'runtime', filename);
 }