We're running it for every single track even if it isn't content sized. Basically we need to keep track of the content-sized tracks and run the algorithm only for them. Fixing this involves merging these two commits from Blink:
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
Review URL: https://chromiumcodereview.appspot.com/22949002
Content-sized resolution should only happen on content-sized tracks
The current code would always try to run the content sized
algorithm regardless of whether this was needed. On top of
it, it would iterate over ALL grid items, even if only a
small set of the tracks were content-sized.
This change stores of which tracks are content-sized and
use the internal grid to only iterate over these tracks.
On a Z620, this speeds up
about 550 runs / sec to 830 runs / sec.
Review URL: https://chromiumcodereview.appspot.com/22867006
Created attachment 217044 [details]
Comment on attachment 217044 [details]
Attachment 217044 [details] did not pass efl-wk2-ews (efl-wk2):
Committed r159684: <http://trac.webkit.org/changeset/159684>