[CherryPick] [Page Visibility API] View-less documents should reports as hidden

[CherryPick] [Page Visibility API] View-less documents should reports as hidden

[Title] [Page Visibility API] View-less documents should reports as hidden
[Problem] P130814-01392, P130814-01387
[Cause] The default value of visibility is true
[Solution] The visibility of the document is inherited from the visibility of the page. If there is no page associated with the document, we will assume that the page is hidden, as specifed by the spec,
http://dvcs.w3.org/hg/webperf/raw-file/tip/specs/PageVisibility/Overview.html#dom-document-hidden

https://bugs.webkit.org/show_bug.cgi?id=99410

Change-Id: Ic1b58eed36fc527d465b15552d972981dce46cae