Add a window property to associate RWHVA with its child AX tree ID

content/browser/frame_host/render_frame_host_impl.cc

Index: content/browser/frame_host/render_frame_host_impl.cc
diff --git a/content/browser/frame_host/render_frame_host_impl.cc b/content/browser/frame_host/render_frame_host_impl.cc
index b6086a04aecf9b994912f9ece06ffcad50fa5b49..73ae825f21cdfee6aa8bb401164373b3dd910ecc 100644
--- a/content/browser/frame_host/render_frame_host_impl.cc
+++ b/content/browser/frame_host/render_frame_host_impl.cc
@@ -1973,6 +1973,9 @@ void RenderFrameHostImpl::OnAccessibilityEvents(
 
   RenderWidgetHostViewBase* view = GetViewForAccessibility();
 
+  if (frame_tree_node_->IsMainFrame() && view)
+    view->SetMainFrameAXTreeID(GetAXTreeID());
+
   AccessibilityMode accessibility_mode = delegate_->GetAccessibilityMode();
   if ((accessibility_mode != AccessibilityModeOff) && view && is_active()) {
     if (accessibility_mode & ACCESSIBILITY_MODE_FLAG_NATIVE_APIS)