Crash on OS X when shift clicking outside of input
https://bugs.webkit.org/show_bug.cgi?id=104058

Patch by Yi Shen <max.hong.shen@gmail.com> on 2013-04-22
Reviewed by Chang Shu.

Source/WebCore:

Shift clicking outside of a focused div while removing the focused div from
the dom tree at the same time may hit a null visible position, which should
not be used to calculate the text distance with the new selection's start and
end position. Otherwise, the browser may crash.

Test: editing/selection/crash-on-shift-click.html

* page/EventHandler.cpp:
(WebCore::EventHandler::handleMousePressEventSingleClick):

LayoutTests:

Add test for shift click crash issue.

* editing/selection/crash-on-shift-click-expected.txt: Added.
* editing/selection/crash-on-shift-click.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148894 268f45cc-cd09-0410-ab3c-d52691b4dbfc