https://bugs.webkit.org/show_bug.cgi?id=127315

Reviewed by Andreas Kling.

Add a UserContentController object to PageGroup and have the page group set it on any
pages that are added to the page group.

This is another step towards moving handling of user content away from PageGroup and make it
possible for each page to have different user content.

* page/Page.cpp:
(WebCore::Page::~Page):
(WebCore::Page::setUserContentController):
* page/Page.h:
(WebCore::Page::userContentController):
* page/PageGroup.cpp:
(WebCore::PageGroup::PageGroup):
(WebCore::PageGroup::addPage):
(WebCore::PageGroup::removePage):
* page/PageGroup.h:
* page/UserContentController.cpp:
(WebCore::UserContentController::addPage):
(WebCore::UserContentController::removePage):
* page/UserContentController.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@162380 268f45cc-cd09-0410-ab3c-d52691b4dbfc