Roll Observatory packages and add a roll script

packages/usage/tool/drone.sh

Index: packages/usage/tool/drone.sh
diff --git a/packages/usage/tool/drone.sh b/packages/usage/tool/drone.sh
new file mode 100755
index 0000000000000000000000000000000000000000..ff46f4fcc4ecbcb1935e49732b18ec2edb28dda9
--- /dev/null
+++ b/packages/usage/tool/drone.sh
@@ -0,0 +1,27 @@
+#!/bin/bash
+
+# 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.
+
+# Fast fail the script on failures.
+set -e
+
+# Display installed versions.
+dart --version
+
+# Get our packages.
+pub get
+
+# Verify that the libraries are error free.
+dartanalyzer --fatal-warnings \
+  lib/usage.dart \
+  lib/usage_html.dart \
+  lib/usage_io.dart \
+  test/all.dart
+
+# Run the tests.
+dart test/all.dart
+
+# Measure the size of the compiled JS, for the dart:html version of the library.
+dart tool/grind.dart build