Unable to reproduce the issue on chrome reported version# 69.0.3497.81 using Ubuntu 17.10 with steps mentioned below:
1) Launched chrome reported version and theme is set to "Classic" and opened few tabs
2) Able to see page title on tab strip, changed theme to "GTK+" and seen page title on tab strip

@Reporter: Please find the attached screencast for your reference and provide your feedback on it. Try to test this issue by creating new person with no apps and extensions in it and let us know if the issue still persists.

Thanks!

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Which GTK theme are you using?

I was using the default GTK+ theme provided by chrome.

Well, I think the recent upgrade kinda messed up a little with the extensions which I had previously installed, causing the issue which I faced. (I haven't checked which one is problematic)

Switching to 'new person' solved my issue. 

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Able to reproduce using the "Blackbird" GTK theme.

 Issue 882668  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3146bd70eac207ad70e79680da7fd66169bf967a

commit 3146bd70eac207ad70e79680da7fd66169bf967a
Author: Tom Anderson <thomasanderson@chromium.org>
Date: Tue Sep 11 18:09:52 2018

[GTK] Add title class to background tab text color selectors

This fixes the background tab text color when using the Blackbird GTK theme.
Blackbird styles titlebar labels with dark text unless the label has the "title"
class [1].  This means creating a label in the titlebar will be illegible on
Blackbird since the frame is dark too.  This is a bug that was probably never
seen since having a non-title label in the frame is rare.

This CL adds ".title" to our selector to get the correct light color on
Blackbird.  Other themes should be unaffected.

[1] https://github.com/shimmerproject/Blackbird/blob/master/gtk-3.20/gtk-widgets.css#L4742

BUG= 881550 
R=pkasting

Change-Id: I16ef16c27ab4500c152bb56a105276be4bbf708a
Reviewed-on: https://chromium-review.googlesource.com/1217146
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590404}
[modify] https://crrev.com/3146bd70eac207ad70e79680da7fd66169bf967a/chrome/browser/ui/libgtkui/gtk_ui.cc

Requesting merge to M69 and M70.  The merge is very small and should be safe.

I realize it would be a post-stable merge to M69.  This does not require a respin, but I'd like this change merged in case we do decide to respin for another issue.

This bug requires manual review: Request affecting a post-stable build
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

Approving merge for M70. Branch:3538

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/47514b1d3133b014955a94c206aceda03e661fe2

commit 47514b1d3133b014955a94c206aceda03e661fe2
Author: Tom Anderson <thomasanderson@chromium.org>
Date: Tue Sep 11 19:37:58 2018

[Merge to M70] [GTK] Add title class to background tab text color selectors

> This fixes the background tab text color when using the Blackbird GTK theme.
> Blackbird styles titlebar labels with dark text unless the label has the "title"
> class [1].  This means creating a label in the titlebar will be illegible on
> Blackbird since the frame is dark too.  This is a bug that was probably never
> seen since having a non-title label in the frame is rare.
>
> This CL adds ".title" to our selector to get the correct light color on
> Blackbird.  Other themes should be unaffected.
>
> [1] https://github.com/shimmerproject/Blackbird/blob/master/gtk-3.20/gtk-widgets.css#L4742
>
> BUG= 881550 
> R=pkasting
>
> Change-Id: I16ef16c27ab4500c152bb56a105276be4bbf708a
> Reviewed-on: https://chromium-review.googlesource.com/1217146
> Reviewed-by: Peter Kasting <pkasting@chromium.org>
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#590404}

BUG= 881550 
TBR=pkasting
NOTRY=true
NOPRESUBMIT=true
NOTREECHECKS=true

Change-Id: Idbd9d750f1e3e898dd0e546205aae7937e990fd0
Reviewed-on: https://chromium-review.googlesource.com/1220483
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/branch-heads/3538@{#286}
Cr-Branched-From: 79f7c91a2b2a2932cd447fa6f865cb6662fa8fa6-refs/heads/master@{#587811}
[modify] https://crrev.com/47514b1d3133b014955a94c206aceda03e661fe2/chrome/browser/ui/libgtkui/gtk_ui.cc

Pls update the bug after verifying it on tomorrow's dev. 

This is P2, applicable to Linux only and M69 has been out at 100% since last Tuesday, pls justify post merge to M69. Thank you.

This bug likely only affects a small percent of users, but it is quite broken for the users it does impact.  The fix should not have any effect on other themes that are not impacted by this issue.

Will post back tomorrow with the verification.

Tried to reproduce the issue on Ubuntu 14.04 on the reported version 69.0.3497.81 and unable to reproduce the issue by following the below steps.

1. Launched Chrome and added 'Blackbird' theme.
2. Opened many tabs and could read the page title on the tab strip without any issues.
Attached is the screen shot for reference.
	
thomasanderson@ Request you to check and confirm if anything is missed from our end in verifying the issue and help us in verifying the fix on the latest M-70 & M-71 builds.

Thanks..

+ screen shot for comment #14

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Verified on 70.0.3538.16

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thomasanderson@, thank you so much for verifying the issue. Appreciate your quick help!

Is this change specific to Linux?

> Is this change specific to Linux?

yes

Approving merge to M69 branch 3497 based on comments #13, #16 and #19. Pls merge ASAP. Thank you.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8ebb2aa6d76ab9ece293a15c5c2a7b184825d47a

commit 8ebb2aa6d76ab9ece293a15c5c2a7b184825d47a
Author: Tom Anderson <thomasanderson@chromium.org>
Date: Thu Sep 13 19:28:55 2018

[Merge to M69] [GTK] Add title class to background tab text color selectors

> This fixes the background tab text color when using the Blackbird GTK theme.
> Blackbird styles titlebar labels with dark text unless the label has the "title"
> class [1].  This means creating a label in the titlebar will be illegible on
> Blackbird since the frame is dark too.  This is a bug that was probably never
> seen since having a non-title label in the frame is rare.
>
> This CL adds ".title" to our selector to get the correct light color on
> Blackbird.  Other themes should be unaffected.
>
> [1] https://github.com/shimmerproject/Blackbird/blob/master/gtk-3.20/gtk-widgets.css#L4742
>
> BUG= 881550 
> R=pkasting
>
> Change-Id: I16ef16c27ab4500c152bb56a105276be4bbf708a
> Reviewed-on: https://chromium-review.googlesource.com/1217146
> Reviewed-by: Peter Kasting <pkasting@chromium.org>
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#590404}

BUG= 881550 
TBR=pkasting
NOTRY=true
NOPRESUBMIT=true
NOTREECHECKS=true

Change-Id: I0d76148465af8faaef9720a1b68fba9d0c250584
Reviewed-on: https://chromium-review.googlesource.com/1224533
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/branch-heads/3497@{#934}
Cr-Branched-From: 271eaf50594eb818c9295dc78d364aea18c82ea8-refs/heads/master@{#576753}
[modify] https://crrev.com/8ebb2aa6d76ab9ece293a15c5c2a7b184825d47a/chrome/browser/ui/libgtkui/gtk_ui.cc

thomasanderson@, this change is merged to M69. Pls verify this bug on M69 build #69.0.3497.96 (currently building) tomorrow morning and update result here. Thank you.

The NextAction date has arrived: 2018-09-14

Verified on 69.0.3497.96

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Adding the verified label for 69.0.3497.100 as I was able to repro the issue on reported version 69.0.3497.81 on Linux Debian Rodete.

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