Roll Observatory packages and add a roll script

packages/barback/test/transformer/check_content_and_rename.dart

+// Copyright (c) 2013, 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 barback.test.transformer.check_content_and_rename;
+
+import 'dart:async';
+
+import 'package:barback/barback.dart';
+
+import 'mock.dart';
+
+/// A transformer that checks the extension and content of an asset, then
+/// produces a new asset with a new extension and new content.
+class CheckContentAndRenameTransformer extends MockTransformer {
+  final String oldExtension;
+  final String oldContent;
+  final String newExtension;
+  final String newContent;
+
+  CheckContentAndRenameTransformer({this.oldExtension, this.oldContent,
+      this.newExtension, this.newContent}) {
+    assert(oldExtension != null);
+    assert(oldContent != null);
+    assert(newExtension != null);
+    assert(newContent != null);
+  }
+
+  bool doIsPrimary(AssetId id) => id.extension == '.$oldExtension';
+
+  Future doApply(Transform transform) {
+    return getPrimary(transform).then((input) {
+      return input.readAsString().then((contents) {
+        if (contents != oldContent) return;
+
+        transform.addOutput(new Asset.fromString(
+            input.id.changeExtension('.$newExtension'), newContent));
+      });
+    });
+  }
+}