commit 0fb20fcf124008c53b2c81fa5ba215391dbc87fa
author Steinar H. Gunderson <sesse@chromium.org> Wed Mar 05 10:43:38 2025
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Wed Mar 05 10:43:38 2025
tree f8d7dc37a8a8b043178a865238f8f1cd2d1449d6
parent bd47ae5105acdbdc816de78a9846fc37e6353dc5

Remove the last mixed-inheritance ComputedStyle groups.

The “svg” group is the only one left that have both inherited
and non-inherited members/subgroups, and thus may need to be
pieced together anew as opposed to just (lazily) copied.
We do some moves to remedy this:

 - Move “svg->svginherited” to the top.
 - Move the other inherited subgroups of “svg” into subgroups
   on “svginherited”.
 - Move Font from the top to “inherited” to not make
   ComputedStyle any bigger. (It was moved to the top at a
   point where Font wasn't on Oilpan and things were generally
   slightly different from today.)

Also add an assertion so that we don't introduce this anew
inadvertently.

We tried a couple of different alternatives (that involved
e.g. not moving Font), but this one seemed to benchmark
slightly better.

Style perftest (Zen 3, LTO but no PGO):

  Initial style (µs)     Before     After    Perf      95% CI (BCa)
  =================== ========= ========= ======= =================
  ECommerce                5532      5446   +1.6%  [ +1.1%,  +2.3%]
  Encyclopedia            43587     43650   -0.1%  [ -1.2%,  +0.9%]
  Extension               57426     56274   +2.0%  [ +1.5%,  +3.3%]
  News                    22293     22156   +0.6%  [ +0.1%,  +1.5%]
  Search                   7734      7640   +1.2%  [ +0.7%,  +2.4%]
  Social1                 14014     13914   +0.7%  [ +0.2%,  +1.5%]
  Social2                  8780      8650   +1.5%  [ +1.0%,  +2.6%]
  Sports                  26458     26285   +0.7%  [ -0.5%,  +1.5%]
  Video                   18143     17814   +1.8%  [ +1.2%,  +3.6%]
  Geometric mean                            +1.1%  [ +0.7%,  +1.5%]

  Recalc style (µs)      Before     After    Perf      95% CI (BCa)
  =================== ========= ========= ======= =================
  ECommerce                3000      2934   +2.2%  [ +1.7%,  +2.9%]
  Encyclopedia            33945     33294   +2.0%  [ +1.3%,  +2.5%]
  Extension               45428     44666   +1.7%  [ +1.1%,  +2.5%]
  News                    11069     10968   +0.9%  [ +0.3%,  +1.5%]
  Search                   2851      2824   +0.9%  [ +0.4%,  +1.6%]
  Social1                  6907      6798   +1.6%  [ +0.7%,  +3.6%]
  Social2                  4291      4225   +1.6%  [ +1.0%,  +2.1%]
  Sports                  12996     12765   +1.8%  [ +1.3%,  +2.4%]
  Video                    7575      7459   +1.5%  [ +0.5%,  +2.5%]
  Geometric mean                            +1.6%  [ +1.2%,  +2.0%]

Speedometer3 (M1 Pinpoint, LTO but no PGO, significant results
at 99% CI only):

  NewsSite-Next                               [ -0.6%,  -0.0%]
  TodoMVC-JavaScript-ES5                      [ -0.5%,  -0.1%]
  TodoMVC-Vue                                 [ -0.6%,  -0.1%]

Change-Id: I8a94056a275b731fe2955aa45c1435bb54101d75
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6321928
Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org>
Commit-Queue: Steinar H Gunderson <sesse@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1428214}