Add browser-compatible version.

lib/browser_resource.dart

Index: lib/browser_resource.dart
diff --git a/lib/resource.dart b/lib/browser_resource.dart
similarity index 66%
copy from lib/resource.dart
copy to lib/browser_resource.dart
index 83c75c695dabd9249317861ec15cbf8691c36cb8..d66eeb31d4584a856255f84d792996a8ccaf3d0f 100644
--- a/lib/resource.dart
+++ b/lib/browser_resource.dart
@@ -1,4 +1,4 @@
-// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2016, 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.
 
@@ -21,9 +21,11 @@
 ///                             .first;
 ///
 ///
-/// Notice: Currently this package requires `dart:io` to do the reading,
-/// so it doesn't work in the browser.
+/// Notice: Currently this library requires `dart:Html` to do the reading,
+/// so it doesn't work outside of a browser.
+/// This library will eventually be mergeded into the `resource.dart` when
+/// features are available to make that possible.
 library resource;
 
-export "src/resource.dart" show Resource;
-export "src/loader.dart" show ResourceLoader;
+export "src/browser/resource.dart" show Resource;
+export "src/browser/loader.dart" show ResourceLoader;