Update :

Chromium bisect info:

You are probably looking for a change made after 600223 (known good), but no later than 600228 (first known bad).

CHANGE-LOG URL:
  
https://chromium.googlesource.com/chromium/src/+log/62f2f8f209a82db0dd5a311eb4f844bddb75c98e..631a939b2b9a02a05cd1db367c7ea7fb17d14f50

Suspecting: https://chromium.googlesource.com/chromium/src/+/177774d57a744b75630cba5507c3bf1ed419aea3

@dpapad: Could you please look into the issue, pardon me if it has nothing to do with your changes and if possible please assign it to concern owner.

Note:
1)Issue is also seen on Windows(7,8,8.1,10 and Linux()14.04 LTS) OS
2)Tried per revision bisect on Windows ,Mac and Linux OS but unable to perform the same since getting "RuntimeError: We don't have enough builds to bisect" error 
3.Hence provided suspect through 'Chromium bisect'

Thank You

As this is a recent regression adding release blocker label for this issue.Please reduce priority or remove if not the case.

Thank You!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ed14eb88e53d20737850c4c5ad464920a1ade5e8

commit ed14eb88e53d20737850c4c5ad464920a1ade5e8
Author: dpapad <dpapad@chromium.org>
Date: Wed Oct 24 01:08:54 2018

Settings UI: Declare implied Polymer categoryHeader property in SiteList.

This fixes missing header text in chrome://settings/content/ subpages, when
Polymer2 is turned on.

Bug:  896621 
Change-Id: I2c153ac69aca9c8e0b536e7af5388e412f9bc183
Reviewed-on: https://chromium-review.googlesource.com/c/1297597
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602202}
[modify] https://crrev.com/ed14eb88e53d20737850c4c5ad464920a1ade5e8/chrome/browser/resources/settings/site_settings/site_list.js

Update : 
Retested above issue on  Win(7,8,8.1,10) MAC(10.13.1,10.13.6,10.14.1)and Linux(14.04 LTS) OS using latest Canary #72.0.3591.0 and issue is fixed,'Allow','Clear on exit' titles are now seen on chrome://settings/content/.

Kindly review the attached screen-cast.

Deleted: Canary_Behaviour#72.0.3591.0 cookiestitle.mov 3.1 MB

	Canary_Behaviour#72.0.3591.0 cookiestitle.mov 3.1 MB View Download