Add page view analytics to Observatory

runtime/observatory/observatory_sources.gypi

 # Copyright (c) 2015, 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.
 
 # This file contains all dart, css, and html sources for Observatory.
 {
   'sources': [
     'lib/app.dart',
     'lib/cli.dart',
     'lib/cpu_profile.dart',
     'lib/debugger.dart',
     'lib/dominator_tree.dart',
     'lib/elements.dart',
     'lib/elements.html',
     'lib/object_graph.dart',
     'lib/service.dart',
     'lib/service_common.dart',
     'lib/service_io.dart',
     'lib/service_html.dart',
+    'lib/src/app/analytics.dart',
     'lib/src/app/application.dart',
     'lib/src/app/chart.dart',
     'lib/src/app/location_manager.dart',
     'lib/src/app/page.dart',
     'lib/src/app/settings.dart',
     'lib/src/app/target_manager.dart',
     'lib/src/app/view_model.dart',
     'lib/src/cli/command.dart',
     'lib/src/cpu_profile/cpu_profile.dart',
     'lib/src/debugger/debugger.dart',
@@ skipping 103 matching lines @@
     'lib/src/elements/img/dart_icon.png',
     'lib/src/elements/img/isolate_icon.png',
     'lib/src/service/object.dart',
     'lib/tracer.dart',
     'lib/utils.dart',
     'web/index.html',
     'web/main.dart',
     'web/favicon.ico',
   ],
 }