GitLab

We now use subtraction when the length in a computed length-percentage
calc is negative.

Discussed in https://github.com/w3c/csswg-drafts/issues/3335

Change-Id: I24822de431059a97cf8f9203950b6d84de72180e
Bug: 904805
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1777843Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Eric Willigers <ericwilligers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#692249}