[mathml] Implement font-family: math and use it for <math> tags.

This CL implements the generic font family name "math" [1] and use
it as the default family for MathML <math> tags in the UA stylesheet
[2]. This is done under a new CSSFontFamilyMath experimental feature
implied by the MathMLCore one. This CL only introduces core logic,
with the expectation that it will be refined later:

- font-family: math is not used to pick a math font on Android since
  no font with an OpenType table are pre-installed [3].

- font-family: math just use the hardcoded "Latin Modern Math" font
  on other platforms. They should be configurable by the users.

Intent to prototype is [4].

[1] https://www.w3.org/TR/css-fonts-4/#valdef-font-family-math
[2] https://w3c.github.io/mathml-core/#the-top-level-math-element
[3] https://github.com/googlefonts/noto-fonts/issues/330
[4] https://groups.google.com/a/chromium.org/g/blink-dev/c/CnQuMzqabqE/m/WlZfKOSpAAAJ

Bugs: 6606, 1228189
Change-Id: I546de83520c74df593260f35f670c076ba774872
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2119534
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Commit-Queue: Frédéric Wang <fwang@igalia.com>
Cr-Commit-Position: refs/heads/main@{#914708}
16 files changed
tree: 3f87645d335372758454fb19494737c1478d4615
  1. android_webview/
  2. apps/
  3. ash/
  4. base/
  5. build/
  6. build_overrides/
  7. buildtools/
  8. cc/
  9. chrome/
  10. chromecast/
  11. chromeos/
  12. cloud_print/
  13. codelabs/
  14. components/
  15. content/
  16. courgette/
  17. crypto/
  18. dbus/
  19. device/
  20. docs/
  21. extensions/
  22. fuchsia/
  23. gin/
  24. google_apis/
  25. google_update/
  26. gpu/
  27. headless/
  28. infra/
  29. ios/
  30. ipc/
  31. jingle/
  32. media/
  33. mojo/
  34. native_client_sdk/
  35. net/
  36. pdf/
  37. ppapi/
  38. printing/
  39. remoting/
  40. rlz/
  41. sandbox/
  42. services/
  43. skia/
  44. sql/
  45. storage/
  46. styleguide/
  47. testing/
  48. third_party/
  49. tools/
  50. ui/
  51. url/
  52. weblayer/
  53. .clang-format
  54. .clang-tidy
  55. .eslintrc.js
  56. .git-blame-ignore-revs
  57. .gitattributes
  58. .gitignore
  59. .gn
  60. .mailmap
  61. .vpython
  62. .vpython3
  63. .yapfignore
  64. AUTHORS
  65. BUILD.gn
  66. CODE_OF_CONDUCT.md
  67. codereview.settings
  68. DEPS
  69. DIR_METADATA
  70. ENG_REVIEW_OWNERS
  71. LICENSE
  72. LICENSE.chromium_os
  73. OWNERS
  74. PRESUBMIT.py
  75. PRESUBMIT_test.py
  76. PRESUBMIT_test_mocks.py
  77. README.md
  78. WATCHLISTS
README.md

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