[Qt] Add Page Visibility API support

https://bugs.webkit.org/show_bug.cgi?id=109422

Patch by Benjamin Dupont <bdupont@nds.com> on 2013-08-06
Reviewed by Simon Hausmann.

* WebCoreSupport/QWebPageAdapter.cpp:
(webPageVisibilityStateToWebCoreVisibilityState):
(webCoreVisibilityStateToWebPageVisibilityState):
(QWebPageAdapter::setVisibilityState):
(QWebPageAdapter::visibilityState):
* WebCoreSupport/QWebPageAdapter.h:
* WidgetApi/qwebpage.cpp:
(QWebPage::setVisibilityState):
(QWebPage::visibilityState):
* WidgetApi/qwebpage.h:
* tests/qwebpage/tst_qwebpage.cpp:
(tst_QWebPage::changeVisibilityState):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@153751 268f45cc-cd09-0410-ab3c-d52691b4dbfc

[Qt] Build fix after r153751

Unreviewed build fix.

Fix build when PAGE_VISIBILITY_API is disabled.

* WebCoreSupport/QWebPageAdapter.cpp:
(QWebPageAdapter::visibilityState):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@153782 268f45cc-cd09-0410-ab3c-d52691b4dbfc
Change-Id: I7c99337a902d7d06cde03107ebf71e3fce430fdf
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@digia.com>