[GTK] fast/frames/frame-dead-region.html crash

[GTK] fast/frames/frame-dead-region.html crash
https://bugs.webkit.org/show_bug.cgi?id=79205

Unreviewed.

Apparently we're not supposed to call willDetachPage from
CachedFrame::destroy.  This call got added in
http://trac.webkit.org/changeset/108428, but it seems to cause a crash.

* loader/FrameLoader.cpp:
(WebCore::FrameLoader::closeAndRemoveChild):
(WebCore::FrameLoader::detachFromParent):
* page/Frame.h:
(WebCore::Frame::detachFromPage):
* page/Page.cpp:
(WebCore::Page::~Page):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108465 268f45cc-cd09-0410-ab3c-d52691b4dbfc