[CSS Grid Layout] Avoid preferred logical widths' recomputations

The code runs the content-sized track sizing algorithm all the time,
which forces a layout even when the track is not content-sized. This
change makes us bail out if we know we don't need to run the
algorithm. Note that it will not help content sized grid tracks.

This speeds up PerformanceTests/Layout/fixed-grid-lots-of-data.html
from ~28.5 run/s to ~585 run/s by avoiding a lot of unneeded layouts.

The baselines change comes from triggering less layouts, which changes
the frame rects between 2 subsequent layouts thus changing the repaint
rectangles.

BUG=225892

Review URL: https://chromiumcodereview.appspot.com/22949002

git-svn-id: svn://svn.chromium.org/blink/trunk@156028 bbb929c8-8fbe-4397-9dbb-9b2b20218538