- Implement loading of .packages files from http.

runtime/bin/builtin.dart

 // Copyright (c) 2012, 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 builtin;
 // NOTE: Do not import 'dart:io' in builtin.
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_internal';
 import 'dart:isolate';
@@ skipping 510 matching lines @@
 
 
 void _asyncLoadError(_LoadRequest req, _LoadError error, StackTrace stack) {
   if (_traceLoading) {
     _log("_asyncLoadError(${req._uri}), error: $error\nstack: $stack");
   }
   if (req._tag == _Dart_kResourceLoad) {
     Completer c = req._context;
     c.completeError(error, stack);
   } else {
-    Uri libraryUri = req._context;
+    String libraryUri = req._context;
     if (req._tag == _Dart_kImportTag) {
       // When importing a library, the libraryUri is the imported
       // uri.
       libraryUri = req._uri;
     }
     _asyncLoadErrorCallback(req._uri, libraryUri, error);
   }
   _finishLoadRequest(req);
 }
 
@@ skipping 210 matching lines @@
 
   return [path, filename, name];
 }
 
 
 // Register callbacks and hooks with the rest of the core libraries.
 _setupHooks() {
   _setupCompleted = true;
   VMLibraryHooks.resourceReadAsBytes = _resourceReadAsBytes;
 }