commit 141e1ea6e22668f4f5e16370132fb7f9d127315c
author Frédéric Wang <fwang@igalia.com> Wed Nov 02 20:55:40 2022
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Wed Nov 02 20:55:40 2022
tree 1ec0dc9d4cea7fe0c84eda34b1581a91c3a0f449
parent 2c86716a423a2fc87c08e72c5a5880febdd203b3

Enable MathMLCore by default

Turn on the runtime flag for MathML Core, which implies special
handling for elements in the MathML namespace:

- Default style and layout of MathML elements as described in [1].
- Expose MathMLElement IDL for MathML elements [2].
- Expose MathML to NSAccessibility and ATK accessibility APIs [3].
- Expose new CSS features (font-family: math [4], math-depth [5],
  math-shift [6], math-style [7], text-transform: math-auto [8]
  display: math [9]).
- Make MathML namespace recognized by SVG's requiredExtensions
  attribute [10].

Additionally, the MathMLCore flag enables a UI for configuring the
default math font in Chrome's font preference menu [11].

Intent to ship was sent in [12] and is conditioned on the fact that
LayoutNGPrinting remains enabled in M109.

The following changes are made to existing tests:

- Expectations for virtual/stable/webexposed are updated to take into account the new web-exposed IDL & CSS features mentioned above. Some of them are guarded by flags implied by MathMLCore, so we actually explicitly turn them on to ensure these tests continue to work when LayoutNG is disabled.

- Tweak a bit the expectation of WebContentsAccessibilityTreeTest#math due to small different when MathML is enabled (`<math>` tag uses `mathMLMath` role, text outside MathML token elements discarded).

- Finally, disable iframe-empty-positioned.html and iframe-aria-hidden.html for WebContentsAccessibilityTreeTest ; existing flakes seem to get worse when MathMLCore is enabled [13] [14].

[1] https://w3c.github.io/mathml-core/
[2] https://w3c.github.io/mathml-core/#dom-and-javascript
[3] https://w3c.github.io/mathml-aam/
[4] https://www.w3.org/TR/css-fonts-4/#valdef-font-family-math
[5] https://w3c.github.io/mathml-core/#propdef-math-depth
[6] https://w3c.github.io/mathml-core/#the-math-shift
[7] https://w3c.github.io/mathml-core/#propdef-math-style
[8] https://w3c.github.io/mathml-core/#new-text-transform-values
[9] https://w3c.github.io/mathml-core/#new-display-math-value
[10] https://w3c.github.io/mathml-core/#html-and-svg
[11] https://docs.google.com/document/d/1bvY_Npe2zLW_705KXdmecsH6P9I9wBMpHRsZ9CxWNOI/edit#heading=h.u9hwm9tp8nuy
[12] https://groups.google.com/a/chromium.org/g/blink-dev/c/n4zf_3FWmAA
[13] crbug.com/1379850
[14] crbug.com/1181596

Bug: 6606, 1321001
Change-Id: Ic8544df581c948e29f7e52d1898f013322b203a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3975674
Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Manuel Rego <rego@igalia.com>
Commit-Queue: Frédéric Wang <fwang@igalia.com>
Cr-Commit-Position: refs/heads/main@{#1066681}