renderStyleOfEnclosingTextNode should update style before using a renderer

renderStyleOfEnclosingTextNode should update style before using a renderer
https://bugs.webkit.org/show_bug.cgi?id=121690

Reviewed by Enrica Casucci.

Merge https://chromium.googlesource.com/chromium/blink/+/65f089545e8c18cb268dfcbe56cba1cd8045527a

When accessing a renderer editing should always make sure that the style has been updated for the node.
Editing calls splitTextNode in a number of places and then accesses the renderer later. This patch is
the first of many to make sure editing always updates the style before attempting to access the renderer
(or style) of a node after calling a mutation method.

* editing/ApplyBlockElementCommand.cpp:
(WebCore::ApplyBlockElementCommand::renderStyleOfEnclosingTextNode):
* editing/ApplyBlockElementCommand.h:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@156180 268f45cc-cd09-0410-ab3c-d52691b4dbfc