add to HistoryItem a way to know if its underlying CachedPage has expired

[Alice Liu]

Add to HistoryItem a way to know if its underlying CachedPage has expired. 

This inevitably touches some existing code that has hard-coded the expiration time for a back/forward PageCached-item to 1800.  
It was okay to have hard-coded these because the FIXMEs made it okay.   Fixmes make everything okay.

[Alice Liu]

Created attachment 189853 [details]
not for review, just running through bots

[Build Bot]

Comment on attachment 189853 [details]
not for review, just running through bots

Attachment 189853 [details] did not pass mac-wk2-ews (mac-wk2):
Output: http://queues.webkit.org/results/16719342

[Alice Liu]

Created attachment 189888 [details]
patch

[Brady Eidson]

Comment on attachment 189888 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=189888&action=review

r+ with that change

> Source/WebCore/history/CachedPage.cpp:56
>      : m_timeStamp(currentTime())
> +    , m_expiration(m_timeStamp + page->settings()->backForwardCacheExpirationInterval())
>      , m_cachedMainFrame(CachedFrame::create(page->mainFrame()))

Could this be m_expirationTime instead?

> Source/WebCore/history/CachedPage.cpp:122
> +bool CachedPage::hasExpired() const
> +{
> +    return currentTime() > m_expiration;
> +}

If it was, this code would read more naturally.

[Alice Liu]

committed r145789