Issue is also seen in Ubuntu 14.04 on enabling 'Overlay scrollbar' flag in chrome://flags.

Bisect info:

Good build:56.0.2895.0
Bad build:56.0.2896.0

Change log Url:
https://chromium.googlesource.com/chromium/src/+log/0f2542893ccc7d1a3ec1e84dbe4895dfff04371d..3d914bde3081131a655b467c1a7a232c7c065007

@bokan : Could you please take a look at this.

The scrollbar is still there but it's entirely white. I'd wager device emulation causes us to use the wrong scrollbar painter.

Just to update, still able to reproduce the issue on Linux Ubuntu using chrome version 57.0.2970.0

bokan@ could you please look into this issue.

Thanks,

Overlay scrollbars are turned off in 57 so this shouldn't block stable.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b50f6446eb79c4aaaac0a5eefdf90d2b4a99ce54

commit b50f6446eb79c4aaaac0a5eefdf90d2b4a99ce54
Author: chaopeng <chaopeng@chromium.org>
Date: Wed May 10 14:41:05 2017

DevTools shows overlay scrollbar for enabled aura overlay scrollbar and mac

DevTools mobile emulator currently does not show android overlay
scrollbar when we enabled aura overlay scrollbar or we use it on Mac.

This issue is caused by we have not set any overlay scrollbar setting
on Mac and have not set solid_color_scrollbar_color when enabled aura
overlay scrollbar.

In this patch, we set default overlay scrollbar same as Android Overlay
Scrollbar for Android and DevTools mobile emulator, Aura Overlay
Scrollbar will override the default settings.

BUG= 673258 

Review-Url: https://codereview.chromium.org/2870733002
Cr-Commit-Position: refs/heads/master@{#470570}

[modify] https://crrev.com/b50f6446eb79c4aaaac0a5eefdf90d2b4a99ce54/content/renderer/gpu/render_widget_compositor.cc

Your change meets the bar and is auto-approved for M59. Please go ahead and merge the CL to branch 3071 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), gkihumba@(ChromeOS), Abdul Syed@(Desktop)

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

Please merge your change to M59 branch 3071 by 4:00 PM PT, Monday (05/15) so we can take it in for next week beta release. Thank you.

This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

If all merges have been completed, please remove any remaining Merge-Approved labels from this issue.

Thanks for your time! To disable nags, add the Disable-Nags label.

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

Can you please merge this ASAP?

The merges have been conflicting and so we've decided to push the launch of the feature back to M60. So this no longer needs a merge, do we need to change the labels?

This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

If all merges have been completed, please remove any remaining Merge-Approved labels from this issue.

Thanks for your time! To disable nags, add the Disable-Nags label.

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

Removing merge-approved as the feature's been disabled in beta branch.

Verified on ChromeOS 9582.0.0, 60.0.3107.0