Implement automatic load of composed/embedded automation trees

ui/accessibility/ax_enums.idl

 // Copyright 2014 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.
 
 // These should be kept in sync with third_party/WebKit/public/web/WebAXEnums.h
 // until the Chromium and Blink trees are merged.
 [camel_case_enum_to_string=true] namespace ui {
 
   // For new entries to the following three enums, also add to
   // chrome/common/extensions/api/automation.idl.
@@ skipping 172 matching lines @@
     title_bar,
     toggle_button,
     toolbar,
     tree_grid,
     tree_item,
     tree,
     unknown,
     tooltip,
     value_indicator,
     web_area,
+    web_view,
     window
   };
 
   // TODO(dmazzoni): switch content/ to use AX_STATE_DISABLED instead of
   // !AX_STATE_ENABLED, and AX_STATE_EDITABLE instead of !AX_STATE_READONLY.
   enum AXState {
     busy,
     checked,
     collapsed,
     default,
@@ skipping 84 matching lines @@
     // Relationships between this element and other elements.
     title_ui_element,
     activedescendant_id,
 
     // Color value for AX_ROLE_COLOR_WELL, each component is 0..255
     color_value_red,
     color_value_green,
     color_value_blue,
 
     // Inline text attributes.
-    text_direction
+    text_direction,
+
+    // Uniquely identifies an AXTree.
+    tree_id,
+
+    // Identifies a child tree which this node hosts.
+    child_tree_id
   };
 
   [cpp_enum_prefix_override="ax_attr"] enum AXFloatAttribute {
     // Document attributes.
     doc_loading_progress,
 
     // Range attributes.
     value_for_range,
     min_value_for_range,
     max_value_for_range
@@ skipping 71 matching lines @@
     word_ends
   };
 
   [cpp_enum_prefix_override="ax"] enum AXTextDirection {
     text_direction_lr,
     text_direction_rl,
     text_direction_tb,
     text_direction_bt
   };
 };