Implement automatic load of composed/embedded automation trees

ui/accessibility/accessibility.gyp

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'chromium_code': 1,
   },
 
   'targets': [
@@ skipping 18 matching lines @@
         'ax_node.cc',
         'ax_node.h',
         'ax_node_data.cc',
         'ax_node_data.h',
         'ax_serializable_tree.cc',
         'ax_serializable_tree.h',
         'ax_text_utils.cc',
         'ax_text_utils.h',
         'ax_tree.cc',
         'ax_tree.h',
+        'ax_tree_id_registry.cc',
+        'ax_tree_id_registry.h',
         'ax_tree_serializer.cc',
         'ax_tree_serializer.h',
         'ax_tree_source.h',
         'ax_tree_update.cc',
         'ax_tree_update.h',
         'ax_view_state.cc',
         'ax_view_state.h',
         'platform/ax_platform_node.cc',
         'platform/ax_platform_node.h',
         'platform/ax_platform_node_base.cc',
@@ skipping 57 matching lines @@
         ],
         'non_compiled_schema_files': [],
         'cc_dir': 'ui/accessibility',
         # TODO(dtseng): Change this once all files under ui/accessibility
         # namespaced under ui::ax.
         'root_namespace': 'ui',
       },
     },
   ],
 }