Frame and page lifetime fixes in WebCore::createWindow
https://bugs.webkit.org/show_bug.cgi?id=132089

Reviewed by Sam Weinig.

Speculative fix because I was unable to reproduce the crash that was
reported with the test case attached to this bug.

* loader/FrameLoader.cpp:
(WebCore::createWindow): Changed code to remove the assumption that calls
out will not destroy the page or frame. Use RefPtr for the frame, and
added early exits if frame->page() becomes null at any point before we
use a page pointer.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@167851 268f45cc-cd09-0410-ab3c-d52691b4dbfc