fixes #221, initial sync*, async, async* implementation

lib/src/multi_package_resolver.dart

 // Copyright (c) 2014, 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 dev_compiler.src.multi_package_resolver;
 
 import 'dart:io';
 
 import 'package:analyzer/src/generated/java_io.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:path/path.dart' show join;
 
 /// A package resolver that supports a non-standard package layout, where
 /// packages with dotted names are expanded to a hierarchy of directories, and
 /// packages can be found on one or more locations.
 class MultiPackageResolver extends UriResolver {
   final List<String> searchPaths;
   MultiPackageResolver(this.searchPaths);
 
   @override
-  Source resolveAbsolute(Uri uri) {
+  Source resolveAbsolute(Uri uri, [Uri actualUri]) {
     var candidates = _expandPath(uri);
     if (candidates == null) return null;
 
     for (var path in candidates) {
       var resolvedPath = _resolve(path);
       if (resolvedPath != null) {
-        return new FileBasedSource(new JavaFile(resolvedPath), uri);
+        return new FileBasedSource(
+            new JavaFile(resolvedPath), actualUri != null ? actualUri : uri);
       }
     }
     return null;
   }
 
   /// Resolve [path] by looking at each prefix in [searchPaths] and returning
   /// the first location where `prefix + path` exists.
   String _resolve(String path) {
     for (var prefix in searchPaths) {
       var resolvedPath = join(prefix, path);
       if (new File(resolvedPath).existsSync()) return resolvedPath;
     }
     return null;
   }
 
   /// Expand `uri.path`, replacing dots in the package name with slashes.
   List<String> _expandPath(Uri uri) {
     if (uri.scheme != 'package') return null;
     var path = uri.path;
     var slashPos = path.indexOf('/');
     var packagePath = path.substring(0, slashPos).replaceAll(".", "/");
     var filePath = path.substring(slashPos + 1);
     return ['$packagePath/lib/$filePath', '$packagePath/$filePath'];
   }
 }