(Most of the added people here are previous owners. Maybe set to Untriaged to get more attention from the new owners.)

Adding the new NTP TL.

I'm assuming you've got this one covered Roman, removing from the Enterprise triage queue.

What's the best way to reproduce / test this (in the dev environment)? 

HideWebStoreIcon is not set, per my chrome://policy - should I edit some file in /etc/chromium/policies/managed (as referenced in https://www.chromium.org/administrators/linux-quick-start)?

Also, just to confirm the policy language ("Hide the Chrome Web Store app and footer link from the New Tab Page"):
- the app is what's listed in chrome://apps
- the footer link is the MV tile, under the fakebox on the NTP

Is that correct?

The footer link is in the bottom right of chrome://apps (which was a part of the NTP long ago). I guess "the app" probably refers to both the app in chrome://apps and the NTP tile.

The easy way to repro on linux is to put chrome.json with
{
  "HideWebStoreIcon": true,
}
into 
/etc/chromium/policies/managed for Chromium or
/etc/opt/chrome/policies/managed/ for Chrome

- the app is what's listed in chrome://apps - Yes, that works ok
- the footer link is the MV tile, under the fakebox on the NTP - seems so

Thanks for the clarifications!

+Yana FYI

When should the policy take effect on the NTP? Are user required to reboot the browser or the policy should take effect immediately on the next NTP?

IMHO, it should take effect right after it changed. You could subscribe to preference change (see https://cs.chromium.org/chromium/src/chrome/browser/ui/webui/ntp/ntp_resource_cache.cc?rcl=888b6b538049e94313396b10aab3f21b5367d7a0&l=150)

The policy will be applied immediately. You can test it either from chrome://policy or from chrome://apps. The policy will affect the prepopulated_list when a new profile opens. The reason why the NTP still shows the webstore even after the policy was changed is because it take advantage of a cached value for the most-visited tile list so that the browser can fetch the most-visited tiles quickly. The policy will not take effect on that profile at once but will do if you open a new profile. 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9a40eecd2435cbeaf76c8362e3f8be8be4810569

commit 9a40eecd2435cbeaf76c8362e3f8be8be4810569
Author: Weilun Shi <sweilun@chromium.org>
Date: Fri Aug 03 23:24:49 2018

[NTP] Update NTP to respect the HideWebStoreIcon policy

Now, changing the HideWebStoreIcon policy will affect the
prepopulated_list when a new profile opens or reopen the browser. The
policy doesn't affect current profile on the NTP. This is because the
browser will cache the prepopulated list so that it can fetch the tiles
quickly.

Bug:  855603 
Change-Id: I99ac05040fc44f64ac61151218dcbcc612465e72
Reviewed-on: https://chromium-review.googlesource.com/1137432
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Weilun Shi <sweilun@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580699}
[modify] https://crrev.com/9a40eecd2435cbeaf76c8362e3f8be8be4810569/chrome/browser/history/top_sites_factory.cc
[modify] https://crrev.com/9a40eecd2435cbeaf76c8362e3f8be8be4810569/chrome/browser/policy/policy_browsertest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bb7292fb64f2dee3224a9eefe4aaa1ae9588ff37

commit bb7292fb64f2dee3224a9eefe4aaa1ae9588ff37
Author: Reid Kleckner <rnk@chromium.org>
Date: Tue Aug 07 00:43:26 2018

Revert "[NTP] Update NTP to respect the HideWebStoreIcon policy"

This reverts commit 9a40eecd2435cbeaf76c8362e3f8be8be4810569.

Reason for revert: Test fails in official builds.

Original change's description:
> [NTP] Update NTP to respect the HideWebStoreIcon policy
> 
> Now, changing the HideWebStoreIcon policy will affect the
> prepopulated_list when a new profile opens or reopen the browser. The
> policy doesn't affect current profile on the NTP. This is because the
> browser will cache the prepopulated list so that it can fetch the tiles
> quickly.
> 
> Bug:  855603 
> Change-Id: I99ac05040fc44f64ac61151218dcbcc612465e72
> Reviewed-on: https://chromium-review.googlesource.com/1137432
> Reviewed-by: Scott Violet <sky@chromium.org>
> Commit-Queue: Weilun Shi <sweilun@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#580699}

TBR=sky@chromium.org,ramyan@chromium.org,sweilun@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug:  855603 , 871166
Change-Id: If88116adf0fdd613ec5c2ede8abeb3c8b6b6207c
Reviewed-on: https://chromium-review.googlesource.com/1164205
Reviewed-by: Reid Kleckner <rnk@chromium.org>
Commit-Queue: Reid Kleckner <rnk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581064}
[modify] https://crrev.com/bb7292fb64f2dee3224a9eefe4aaa1ae9588ff37/chrome/browser/history/top_sites_factory.cc
[modify] https://crrev.com/bb7292fb64f2dee3224a9eefe4aaa1ae9588ff37/chrome/browser/policy/policy_browsertest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b59ba593809427b54375bc5f885fa74c39f638ee

commit b59ba593809427b54375bc5f885fa74c39f638ee
Author: Weilun Shi <sweilun@chromium.org>
Date: Tue Aug 07 22:42:35 2018

[NTP] Update NTP to respect the HideWebStoreIcon policy and enable NTP MD feature for HiddenWebStoreIcon test

Now, Changing the HideWebStoreIcon policy will affect the
prepopulated_list when a new profile opens or reopen the browser. The
policy doesn't affect current profile on the NTP. This is because the
browser will cache the prepopulated list so that it can fetch the tiles
quickly. Also, force to enable New Tab Page Material Design flag for the
HiddenWebStoreIcon test so that the PolicyTest can now get the new
md-tile element instead of the old mv-tile.

Bug: 871166,  855603 
Change-Id: I77a632daa73d655d9d1df053186782917405a15b
Reviewed-on: https://chromium-review.googlesource.com/1164077
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Weilun Shi <sweilun@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581378}
[modify] https://crrev.com/b59ba593809427b54375bc5f885fa74c39f638ee/chrome/browser/history/top_sites_factory.cc
[modify] https://crrev.com/b59ba593809427b54375bc5f885fa74c39f638ee/chrome/browser/policy/policy_browsertest.cc

Checked using yaps on Google Chrome 69.0.3497.36 Platform 10895.25.0 coral-santa

Observation:
1. With HideWebStoreIcon policy not set -> "Chrome web store app" is shown in app list.
2. With HideWebStoreIcon policy true ->  "Chrome web store app" is not shown in app list.

However, the Chrome Webstore thumbnail is seen on new tab recent list.

Please confirm if this is expected as per fix. Thanks.!

Deleted: Screenshot 2018-08-14 at 1.16.55 PM.png 81.1 KB

	Screenshot 2018-08-14 at 1.16.55 PM.png 81.1 KB View Download

It _is_ expected behavior if the policy went into effect after the webstore icon was presented on the profile & the user has visited the page because the item becomes part of the profile's history. 

However, it should not happen for profiles created after the policy went into effect.

Thank you :) Closing the bug as verified.