Merge 129814 - REGRESSION(r129186): Pressing enter at the end of a line deletes the line

Merge 129814 - REGRESSION(r129186): Pressing enter at the end of a line deletes the line
https://bugs.webkit.org/show_bug.cgi?id=97763

Reviewed by Ryosuke Niwa.

r129186 exposed incorrect behavior in RenderText whereby RenderText's lines were
dirtied but the renderer wasn't marked for layout. Rich text editing in GMail exposed
this behavior. RenderText::setTextWithOffset is called with a text string identical
to the current text. It still dirties lines, then calls setText, which has a check
for the case when the strings are the same and returns early and doesn't mark us as
needing layout.

This change adds the same early bailing logic in setText to setTextWithOffset, but
forces setText to work its magic whenever we dirty lines there (and avoid double-
checking that the strings are equal).

* rendering/RenderText.cpp:
(WebCore::RenderText::setTextWithOffset):


TBR=leviw@chromium.org
Committed: https://trac.webkit.org/changeset/129818