On the web, if you set position:absolute, but not
top/right/bottom/left, then the absolute goes where it
would have gone if it wasn't positioned. The use-cases for
this are slim and it introduces a lot of complexity to the
engine.
Also changes behavior in the presence of direction:rtl.
On the web, direction:rtl and top/left:auto would
sometimes set right:0. Instead we always position at
0,0 if the opposing values are auto.
This removes the code for this positioning and allows
simplifying a bunch of dirty bit handling code since
we don't need to setNeedsLayout if lines move around
or wrap differently.
The test cases did change their output, but the new
positioning all looks correct to me.
Review URL: https://codereview.chromium.org/944073006
