Try |View::HandleAccessibleAction| before falling back to fixed actions.

chrome/browser/ui/aura/accessibility/ax_tree_source_aura.cc

 // 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.
 
 #include "chrome/browser/ui/aura/accessibility/ax_tree_source_aura.h"
 
 #include <stddef.h>
 
 #include <vector>
 
@@ skipping 43 matching lines @@
   if (obj)
     obj->SetSelection(start, end);
 }
 
 void AXTreeSourceAura::ShowContextMenu(int32_t id) {
   AXAuraObjWrapper* obj = AXAuraObjCache::GetInstance()->Get(id);
   if (obj)
     obj->ShowContextMenu();
 }
 
+bool AXTreeSourceAura::HandleAccessibleAction(const ui::AXActionData& action) {
+  AXAuraObjWrapper* obj =
+      AXAuraObjCache::GetInstance()->Get(action.target_node_id);
+  if (obj)
+    return obj->HandleAccessibleAction(action);
+  return false;
+}
+
 bool AXTreeSourceAura::GetTreeData(ui::AXTreeData* tree_data) const {
   tree_data->tree_id = 0;
   tree_data->loaded = true;
   tree_data->loading_progress = 1.0;
   AXAuraObjWrapper* focus = AXAuraObjCache::GetInstance()->GetFocus();
   if (focus)
     tree_data->focus_id = focus->GetID();
   return true;
 }
 
@@ skipping 64 matching lines @@
 
   std::vector<AXAuraObjWrapper*> children;
   root->GetChildren(&children);
 
   prefix += prefix[0];
   for (size_t i = 0; i < children.size(); ++i)
     output += ToString(children[i], prefix);
 
   return output;
 }