[Webkit-unassigned] [Bug 123989] New: [CSS Grid Layout] Speed up content sized track layout

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=123989

           Summary: [CSS Grid Layout] Speed up content sized track layout
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Keywords: BlinkMergeCandidate
          Severity: Normal
          Priority: P2
         Component: CSS
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: svillar at igalia.com
                CC: koivisto at iki.fi, xan.lopez at gmail.com,
                    rniwa at webkit.org, akling at apple.com


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

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