Prevent browser-side hit testing when page popup is selected

content/browser/renderer_host/render_widget_host_view_event_handler.cc

Index: content/browser/renderer_host/render_widget_host_view_event_handler.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_event_handler.cc b/content/browser/renderer_host/render_widget_host_view_event_handler.cc
index f00420c1ee93afcd5c87c995fc61dc5a48e405c8..578464f2339af02ee4c3d43e606f671c8aca5e6b 100644
--- a/content/browser/renderer_host/render_widget_host_view_event_handler.cc
+++ b/content/browser/renderer_host/render_widget_host_view_event_handler.cc
@@ -850,6 +850,13 @@ bool RenderWidgetHostViewEventHandler::ShouldRouteEvent(
   //    in a similar manner to RenderWidgetHostViewGuest.
   bool result = host_->delegate() && host_->delegate()->GetInputEventRouter() &&
                 !disable_input_event_router_for_testing_;
+
+  // Do not route events that are currently targeted to page popups such as
+  // <select> element drop-downs, since these cannot contain cross-process
+  // frames.
+  if (host_->delegate() && !host_->delegate()->IsWidgetForMainFrame(host_))
+    return false;
+
   // ScrollEvents get transformed into MouseWheel events, and so are treated
   // the same as mouse events for routing purposes.
   if (event->IsMouseEvent() || event->type() == ui::ET_SCROLL)