The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c137228e8d1021ceba4eb7bf03e6492fe6c62256

commit c137228e8d1021ceba4eb7bf03e6492fe6c62256
Author: Tom Anderson <thomasanderson@chromium.org>
Date: Tue Aug 21 23:51:34 2018

GTK: Supply COLOR_BACKGROUND_TAB* theme colors

BUG= 876451 
R=pkasting

Change-Id: I2be8079b64ef0f05fbb740dc99562f44a1734fab
Reviewed-on: https://chromium-review.googlesource.com/1184045
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584928}
[modify] https://crrev.com/c137228e8d1021ceba4eb7bf03e6492fe6c62256/chrome/browser/ui/libgtkui/gtk_ui.cc

Requesting merge of CL in c#1 to M69.  The CL should be safe and only affects Linux.

This bug requires manual review: We are only 12 days from stable.
Please contact the milestone owner if you have questions.
Owners: amineer@(Android), kariahda@(iOS), cindyb@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Pls update bug with canary result tomorrow. 
Also may I pls know why multiple merge requests coming this late in release cycle?

I'm sure you're aware already, but there were some large UI changes targeted for M69.  We just keep finding new bugs with the new design so we keep having to fix them ¯\_(ツ)_/¯  This bug is fairly minor, however.

Yeah, understood. I'm just trying to minimize the merges as we're getting very close to stable promotion. 

As per comment #2, this is safe and only affects Linux so I will approve the merge after you verify it on canary tomorrow. Thank you.

The NextAction date has arrived: 2018-08-22

Verified on 70.0.3530.0

Deleted: Screenshot from 2018-08-22 11-38-36.png 253 KB

	Screenshot from 2018-08-22 11-38-36.png 253 KB View Download

Approving merge to M69 branch 3497 based on comment #8. Pls merge now. Thank you.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e2f9357845d0017c772c572273e3739513578ef2

commit e2f9357845d0017c772c572273e3739513578ef2
Author: Tom Anderson <thomasanderson@chromium.org>
Date: Wed Aug 22 18:52:54 2018

[Merge to M69] GTK: Supply COLOR_BACKGROUND_TAB* theme colors

> BUG= 876451 
> R=pkasting
>
> Change-Id: I2be8079b64ef0f05fbb740dc99562f44a1734fab
> Reviewed-on: https://chromium-review.googlesource.com/1184045
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Reviewed-by: Peter Kasting <pkasting@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#584928}

BUG= 876451 
TBR=pkasting
NOTRY=true
NOPRESUBMIT=true
NOTREECHECKS=true

Change-Id: I30bd568bcce68f893ebf5e4e4efefe1de73e1647
Reviewed-on: https://chromium-review.googlesource.com/1185530
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/branch-heads/3497@{#774}
Cr-Branched-From: 271eaf50594eb818c9295dc78d364aea18c82ea8-refs/heads/master@{#576753}
[modify] https://crrev.com/e2f9357845d0017c772c572273e3739513578ef2/chrome/browser/ui/libgtkui/gtk_ui.cc

Tried testing the issue on ubuntu 17.10 using chrome version #69.0.3497.57 as per the comment #0.
Attaching screen cast for reference.
Did not observe any difference in chrome reported version #70.0.3521.2 and chrome version #69.0.3497.57. Observed that background inactive tabs are 100% transparent in both the versions.

thomasanderson@ - Could you please check the attached screen cast and please let us know if anything missed from our end in verifying the fix.

Thanks...!!

Deleted: 876451.webm 3.0 MB

	876451.webm 3.0 MB View Download

Please see c#8 for the verification

Verified on 69.0.3497.57 Beta

Deleted: Screenshot from 2018-08-23 10-28-10.png 256 KB

	Screenshot from 2018-08-23 10-28-10.png 256 KB View Download