Issue 832502  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9c091e70ea87966467d96cc1f9444b175a76c8a9

commit 9c091e70ea87966467d96cc1f9444b175a76c8a9
Author: Chris Nardi <cnardi@chromium.org>
Date: Thu Apr 26 17:59:00 2018

Accept two values in the overflow shorthand

https://github.com/w3c/csswg-drafts/issues/2484 details the resolution
by the CSSWG to accept two values in the overflow shorthand. Update our
implementation to match this, and also update two existing CSSOM
serialization tests. Additionally remove tests that are duplicates of
those currently found in WPT.

Intent to Implement and Ship:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/4qF8XPQ1z2s

Bug:  833105 
Change-Id: Id8f61182a7d7369a2f575acfdbf608600d1218dd
Reviewed-on: https://chromium-review.googlesource.com/1013618
Commit-Queue: Chris Nardi <cnardi@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#554078}
[delete] https://crrev.com/e45547a3e00734bd44bc1cb4c37a5450f1dacd81/third_party/WebKit/LayoutTests/external/wpt/css/css-overflow/overflow-shorthand-001-expected.txt
[delete] https://crrev.com/e45547a3e00734bd44bc1cb4c37a5450f1dacd81/third_party/WebKit/LayoutTests/external/wpt/css/cssom/index-002-expected.txt
[modify] https://crrev.com/9c091e70ea87966467d96cc1f9444b175a76c8a9/third_party/WebKit/LayoutTests/external/wpt/css/cssom/overflow-serialization.html
[modify] https://crrev.com/9c091e70ea87966467d96cc1f9444b175a76c8a9/third_party/WebKit/LayoutTests/external/wpt/css/cssom/shorthand-values.html
[modify] https://crrev.com/9c091e70ea87966467d96cc1f9444b175a76c8a9/third_party/WebKit/LayoutTests/fast/css/cssText-shorthand.html
[delete] https://crrev.com/e45547a3e00734bd44bc1cb4c37a5450f1dacd81/third_party/WebKit/LayoutTests/fast/css/different-overflow-x-and-y.html
[modify] https://crrev.com/9c091e70ea87966467d96cc1f9444b175a76c8a9/third_party/WebKit/LayoutTests/fast/css/invalidation-errors-2.html
[modify] https://crrev.com/9c091e70ea87966467d96cc1f9444b175a76c8a9/third_party/WebKit/LayoutTests/fast/css/invalidation-errors.html
[modify] https://crrev.com/9c091e70ea87966467d96cc1f9444b175a76c8a9/third_party/WebKit/LayoutTests/fast/css/overflow-property-expected.txt
[modify] https://crrev.com/9c091e70ea87966467d96cc1f9444b175a76c8a9/third_party/WebKit/LayoutTests/fast/css/overflow-property.html
[modify] https://crrev.com/9c091e70ea87966467d96cc1f9444b175a76c8a9/third_party/blink/renderer/core/css/properties/shorthands/overflow_custom.cc
[modify] https://crrev.com/9c091e70ea87966467d96cc1f9444b175a76c8a9/third_party/blink/renderer/core/css/style_property_serializer.cc