Re-land: 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 e45acd1073e2a2cca3802358d54bc2e82cbee45e..11cebcde9f7a3a12c4c5c54b23c768dea2c17c8d 100644
--- a/content/browser/frame_host/render_frame_host_impl.cc
+++ b/content/browser/frame_host/render_frame_host_impl.cc
@@ -2101,6 +2101,9 @@ void RenderFrameHostImpl::OnAccessibilityEvents(
 
   RenderWidgetHostViewBase* view = GetViewForAccessibility();
 
+  if (frame_tree_node_->IsMainFrame() && view)
+    view->SetMainFrameAXTreeID(GetAXTreeID());
+
   AccessibilityMode accessibility_mode = delegate_->GetAccessibilityMode();
   if (!accessibility_mode.is_mode_off() && view && is_active()) {
     if (accessibility_mode.has_mode(AccessibilityMode::kNativeAPIs))