localStorage events are not passed between WebViews

localStorage events are not passed between WebViews. To reproduce, run a JavaFX application with two WebView instances, open e.g. http://html5demos.com/storage-events or http://www.ellipsetours.com/Demos/storage/ in both instances, do something in one instance, and note that the other instance does not reflect your changes as it should.

The problem is, currently every WebCore::Page object is placed in a separate WebCore::PageGroup. As WebKit broadcasts every storage event within its source page group only, no WebCore::Page and, hence, WebView instance, can receive storage events from other instances.

The proposed solution is to put all WebCore::Page instances with the same userDataDirectory into the same page group, using the following method:

    WebCore::Page::setGroupName(const String& name)

The canonicalized path to the userDataDirectory can become the name of the page group.