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

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

Index: chrome/browser/ui/aura/accessibility/ax_tree_source_aura.cc
diff --git a/chrome/browser/ui/aura/accessibility/ax_tree_source_aura.cc b/chrome/browser/ui/aura/accessibility/ax_tree_source_aura.cc
index 1d86b11284a7020fabbd9c93d57d310dd8d0abec..b390afda5948edc3874025a50ceba4e6182dacdc 100644
--- a/chrome/browser/ui/aura/accessibility/ax_tree_source_aura.cc
+++ b/chrome/browser/ui/aura/accessibility/ax_tree_source_aura.cc
@@ -61,6 +61,14 @@ void AXTreeSourceAura::ShowContextMenu(int32_t id) {
     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;