In RenderViewHostImpl::ExecutePluginActionAtLocation(), coordinates sent from a context menu to a (browsertag) WebView need to be converted from root-view coordinates to the guest-view's coordinate.

It seems likely that this also needs to be done for OOPIFs generally, in both *AtLocation() methods.

If it is needed, this likely involves implementing TransformRootPointToViewCoordSpace for RenderWidgetHostViewChildFrame, and using it in ExecuteMediaPlayerActionAtLocation() as well.