[webkit-help] In what situation will current history item be null ?

[刘凡超]

Hi, guys,
I met some web pages containing sub-frames can't cache in page cache
(which can't navigate between pages without network connection). I
found that these sub-frames do not have current history item
(frameLoader->history()->currentItem() == NULL). I got lost in the
ocean of sources,  so I'd like to know in what situation will current
history item be null? Thanks.

 -- LFC