Assertion failure in WebCore::BidiRun::BidiRun()

Assertion failure in WebCore::BidiRun::BidiRun()
https://bugs.webkit.org/show_bug.cgi?id=145203
rdar://problem/20958973

Reviewed by Andreas Kling.

Source/WebCore:

Test: fast/text/text-combine-crash.html

* rendering/line/BreakingContext.h:
(WebCore::BreakingContext::handleText):

    Renove !isCombined() check. RenderCombineText::combineText() doesn't
    do any work unless needed and text may become uncombined too.

* rendering/line/LineBreaker.cpp:
(WebCore::LineBreaker::skipLeadingWhitespace):

    Same here.

LayoutTests:

* fast/text/text-combine-crash-expected.txt: Added.
* fast/text/text-combine-crash.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@184653 268f45cc-cd09-0410-ab3c-d52691b4dbfc