Crash in deleteInsignificantText

Crash in deleteInsignificantText
https://bugs.webkit.org/show_bug.cgi?id=78567

Reviewed by Eric Seidel.

Source/WebCore:

Fix the crash. Also update layout at the beginning of each call to deleteInsignificantText
since the previous call may have mutated the DOM.

Test: editing/inserting/delete-insignificant-text-crash.html

* editing/CompositeEditCommand.cpp:
(WebCore::CompositeEditCommand::deleteInsignificantText):

LayoutTests:

Add a regression test.

* editing/inserting/delete-insignificant-text-crash.html: Added.
* editing/inserting/delete-insignificant-text-crash.txt: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@107761 268f45cc-cd09-0410-ab3c-d52691b4dbfc