Add memory-dashboard page to Observatory

runtime/observatory/observatory_sources.gypi

 # Copyright (c) 2017, 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/allocation_profile.dart',
     'lib/app.dart',
     'lib/cli.dart',
@@ skipping 74 matching lines @@
     'lib/src/elements/isolate_ref.dart',
     'lib/src/elements/isolate_view.dart',
     'lib/src/elements/json_view.dart',
     'lib/src/elements/library_ref.dart',
     'lib/src/elements/library_view.dart',
     'lib/src/elements/local_var_descriptors_ref.dart',
     'lib/src/elements/logging.dart',
     'lib/src/elements/logging_list.dart',
     'lib/src/elements/megamorphiccache_ref.dart',
     'lib/src/elements/megamorphiccache_view.dart',
-    'lib/src/elements/memory_dashboard.dart',
+    'lib/src/elements/memory/dashboard.dart',
+    'lib/src/elements/memory/graph.dart',
+    'lib/src/elements/memory/profile.dart',
     'lib/src/elements/metric/details.dart',
     'lib/src/elements/metric/graph.dart',
     'lib/src/elements/metrics.dart',
     'lib/src/elements/native_memory_profiler.dart',
     'lib/src/elements/nav/class_menu.dart',
     'lib/src/elements/nav/isolate_menu.dart',
     'lib/src/elements/nav/library_menu.dart',
     'lib/src/elements/nav/menu_item.dart',
     'lib/src/elements/nav/notify.dart',
     'lib/src/elements/nav/notify_event.dart',
@@ skipping 165 matching lines @@
     'lib/utils.dart',
     'web/favicon.ico',
     'web/index.html',
     'web/main.dart',
     'web/third_party/trace_viewer_full.html',
     'web/timeline.html',
     'web/timeline.js',
     'web/timeline_message_handler.js',
   ]
 }