Don't create unneeded layers for scrollbar-gutter: force

This CL prevents the creation of unnecessary layers for elements
that use scrollbar-gutter's "force" keyword.

Now those layers are created only when the element's style uses
custom scrollbars, because a PaintLayerScrollableArea is required
in order to calculate their thickness.

When the element uses default scrollbars, their thickness can be
obtained directly from the page's scrollbar theme.

Bug: 710214
Change-Id: Ia319e5601745247189be58da8b1e992a34a17c99
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2738895
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Felipe Erias <felipeerias@igalia.com>
Cr-Commit-Position: refs/heads/master@{#864254}
6 files changed
tree: 3308b30c764d1b1f0031a27c6f06eea2beea170a
  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. .vpython
  61. .vpython3
  62. .yapfignore
  63. AUTHORS
  64. BUILD.gn
  65. CODE_OF_CONDUCT.md
  66. codereview.settings
  67. DEPS
  68. DIR_METADATA
  69. ENG_REVIEW_OWNERS
  70. LICENSE
  71. LICENSE.chromium_os
  72. OWNERS
  73. PRESUBMIT.py
  74. PRESUBMIT_test.py
  75. PRESUBMIT_test_mocks.py
  76. README.md
  77. WATCHLISTS
README.md

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