Roll Observatory packages and add a roll script

packages/usage/lib/usage_html.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.
 
 /**
  * In order to use this library import the `usage_html.dart` file and
  * instantiate the [AnalyticsHtml] class.
  *
  * You'll need to provide a Google Analytics tracking ID, the application name,
  * and the application version.
@@ skipping 19 matching lines @@
       applicationName: applicationName,
       applicationVersion: applicationVersion) {
     int screenWidth = window.screen.width;
     int screenHeight = window.screen.height;
 
     setSessionValue('sr', '${screenWidth}x$screenHeight');
     setSessionValue('sd', '${window.screen.pixelDepth}-bits');
     setSessionValue('ul', window.navigator.language);
   }
 }