Don't layout absolute-pos element when it's only moved

If an absolute-pos element with specified left or right and auto width
is moved vertically, the original code incorrectly treats the move as
a resize causing unnecessary layout.

Should check if left or right actually changed in the movement check.

BUG=328594
TEST=fast/repaint/absolute-layer-specified-left-or-right-auto-width-moved-vertically.html

Review URL: https://codereview.chromium.org/157093003

git-svn-id: svn://svn.chromium.org/blink/trunk@166878 bbb929c8-8fbe-4397-9dbb-9b2b20218538