I'd like to take this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d7d67f8ba83ef9186aa189777cc78916255aa5f1

commit d7d67f8ba83ef9186aa189777cc78916255aa5f1
Author: Amos Lim <eui-sang.lim@samsung.com>
Date: Fri Nov 16 09:31:39 2018

css: Drop zero value for y of serialization of 2d translate

If a 2d translation is specified, the property must serialize with
only one or two values (per usual, if the second value is 0px, the default,
it must be omitted when serializing)[1].

[1]: https://drafts.csswg.org/css-transforms-2/#individual-transform-serialization

Bug:  904804 
Change-Id: I34c4f47b5413348c7526b9050c89ec35212c3093
Reviewed-on: https://chromium-review.googlesource.com/c/1337670
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Amos Lim <eui-sang.lim@samsung.com>
Cr-Commit-Position: refs/heads/master@{#608708}
[delete] https://crrev.com/857fa233270ec7be0f42dd6520c7b333bc79199b/third_party/WebKit/LayoutTests/external/wpt/css/css-transforms/parsing/translate-parsing-valid-expected.txt
[modify] https://crrev.com/d7d67f8ba83ef9186aa189777cc78916255aa5f1/third_party/blink/renderer/core/css/properties/longhands/translate_custom.cc