REGRESSION (r155957): Invalid cast in WebCore::RenderNamedFlowThread::getRanges
https://bugs.webkit.org/show_bug.cgi?id=134888

Reviewed by Mihnea Ovidenie.


Source/WebCore: 
Test: fast/regions/flowthread-getranges-box-cast.html

* rendering/RenderNamedFlowThread.cpp:
(WebCore::RenderNamedFlowThread::getRanges): Test the type before casting.

LayoutTests: 
* fast/regions/flowthread-getranges-box-cast-expected.txt: Added.
* fast/regions/flowthread-getranges-box-cast.html: Added.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@171105 268f45cc-cd09-0410-ab3c-d52691b4dbfc