Bug 1492964 [wpt PR 13120] - [css-properties-values-api] Use inherited value for...

Bug 1492964 [wpt PR 13120] - [css-properties-values-api] Use inherited value for substitution., a=testonly

Automatic update from web-platform-tests[css-properties-values-api] Use inherited value for substitution.

When a var()-reference produces tokens that are incompatible with the
current syntax, or the var()-reference refers to a variable that does not
exist, we currently always substitute the initial value, even for
inherited properties. This is incorrect, as the value should behave as
'unset', which means 'inherit' for inherited properties.

Note that if syntax-incompatible tokens are specified directly (not via a
var()-reference), we correctly behave as 'unset'. This is because the
var()-less case is handled by a different code path (variable.cc).

R=futhark@chromium.org

Bug: 641877
Change-Id: Ifdd5435ee77f4b8cd3998967713cb6fcb7e8d5f4
Reviewed-on: https://chromium-review.googlesource.com/1235579
Commit-Queue: Anders Ruud <andruud@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593145}

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wpt-commits: 689968f390a8c5c897ab5c9fa0f6fe27a40b5cc3
wpt-pr: 13120