Use correct offset when attribute auto is present

Depending on the inlineBox bidiLevel use the right or left offset.
Do not use bidiLevel of the previous box when attribute is auto.

R=eseidel, leviw
BUG=296847
TEST=TextArea with strong RTL word, when on next line LTR word is
entered, caret position is changed.

Review URL: https://codereview.chromium.org/302433015

git-svn-id: svn://svn.chromium.org/blink/trunk@176151 bbb929c8-8fbe-4397-9dbb-9b2b20218538