This involves merging the following patches from Blink: * [CSS Grid Layout] Speed up content sized track layout This change narrows down the relayout condition in RenderGrid::logicalContentHeightForChild to only percentage children: as they are the only lengths that depends on the containing block's override. We unfortunately can't use percentHeightDescendants as it's not populated yet. This code can probably be simplified further down but it's a good start. This greatly speeds up the new performance test, moving from 25 runs/sec to 91 runs/sec. BUG=234211 Review URL: https://chromiumcodereview.appspot.com/22983004 * [CSS Grid Layout] Cache track breadth min/max content types Profiling shows we repeatedly hit the GridLength isLength() method and the is{Min,Max}Content() methods of the actual Length object. By caching this information, which won't change until we set again the grid lengths, we can improve the auto-grid-lots-of-data.html test by about a 6% (39 runs/s -> 41.5 runs/s). BUG=234211 Review URL: https://codereview.chromium.org/28053003 * [CSS Grid] Do not grow grid tracks when the growth factor has 0 length RenderGrid::distributeSpaceToTracks is by far the hottest method in the auto-grid-lots-of-data.html performance test. By reducing useless "growing" of grid tracks when the growth factor is zero we can improve the test time by 3.55% (422 runs/s -> 437 runs/s). BUG=234211 Review URL: https://codereview.chromium.org/48573002
Added a dependency because the third patch needs the changes from bug 123994.
Actually I'm going to transform this in a meta bug as there are several potential optimizations that will be better handled in different bugs.
Some other potential merges: Remove an extra relayout for non-percent logical height grid items The only reason for a grid item to force a relayout after a grid area's logical height change is if it has a percentage height. In all other cases, this would cause an unneeded relayout. Note that changing the logical width still forces a relayout as the situation is not that simple. This improves auto-grid-lots-of-data.html from 94 runs/s to 226 runs/s as we avoid a relayout in layoutGridItems for every grid items. BUG=273238 Review URL: https://chromiumcodereview.appspot.com/23694023 and 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 PerformanceTests/Layout/fixed-grid-lots-of-data.html from about 550 runs / sec to 830 runs / sec. BUG=273238 Review URL: https://chromiumcodereview.appspot.com/22867006
And also: 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
Added bug 123995 to the list of dependencies
I'm closing this as all the dependencies have landed.