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

chrome/browser/ui/aura/accessibility/automation_manager_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/automation_manager_aura.h"
 
 #include <stddef.h>
 
 #include "base/memory/singleton.h"
 #include "build/build_config.h"
@@ skipping 67 matching lines @@
   views::AXAuraObjWrapper* obj =
       static_cast<AXRootObjWrapper*>(current_tree_->GetRoot())
           ->GetAlertForText(text);
   SendEvent(context, obj, ui::AX_EVENT_ALERT);
 }
 
 void AutomationManagerAura::PerformAction(
     const ui::AXActionData& data) {
   CHECK(enabled_);
 
+  if (current_tree_->HandleAccessibleAction(data)) {
+    // This accessible action is handled by custom action implemented by the
+    // target view.
+    return;
+  }
+
   switch (data.action) {
     case ui::AX_ACTION_DO_DEFAULT:
       current_tree_->DoDefault(data.target_node_id);
       break;
     case ui::AX_ACTION_FOCUS:
       current_tree_->Focus(data.target_node_id);
       break;
     case ui::AX_ACTION_SCROLL_TO_MAKE_VISIBLE:
       current_tree_->MakeVisible(data.target_node_id);
       break;
@@ skipping 98 matching lines @@
 
   processing_events_ = false;
   auto pending_events_copy = pending_events_;
   pending_events_.clear();
   for (size_t i = 0; i < pending_events_copy.size(); ++i) {
     SendEvent(context,
               pending_events_copy[i].first,
               pending_events_copy[i].second);
   }
 }