1689306 - [wpt-sync] Sync PR 27364 - Initial implementation of scrollbar-width

Status: RESOLVED INVALID

(Core :: Layout: Scrolling and Overflow, task, P4)

Description

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Sync web-platform-tests PR 27364 into mozilla-central (this bug is closed when the sync is complete).

PR: https://github.com/web-platform-tests/wpt/pull/27364
Details from upstream follow.

b'Felipe Erias <[e-mail]>' wrote:

Initial implementation of scrollbar-width

ScrollbarTheme::ScrollbarThickness() takes scrollbar-width into
account when calculating the thickness.

Scrollbar themes return a thickness of 0 if scrollbar-width is "none"
and the same value for both "auto" and "thin", with the exception
of ScrollbarThemeMac which uses NSSmallControlSize and
NSRegularControlSize to size and display the appropriate scrollbar.

ComputedStyle::HasCustomScrollbarStyle() returns true if a custom
style for the scrollbar has been set via ::-webkit-scrollbar and
the value of scrollbar-width has not been changed from the default.
This method replaces HasPseudoElementStyle(kPseudoIdScrollbar)
throughout the codebase so the standard properties for styling
scrollbars take precedence over the non-standard method.

WPT tests are included.

Bug: 891944
Change-Id: I9f77d46fc1b05a8d05bb4eeffeef4f8e52f8031b

Reviewed-on: https://chromium-review.googlesource.com/2624189
WPT-Export-Revision: f6dfdd84ac22ad1428719fb98af0adb024c2ab67