Steps to reproduce:

enable slim-navigation-manager
open ntp, and kill the app
start app, tap 'restore'

I don't know enough about this DCHECK to know if this is an issue with slimnav, or this is expected.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1b6cda4e53ceec22638d07060bdb97008d97626e

commit 1b6cda4e53ceec22638d07060bdb97008d97626e
Author: Yi Su <mrsuyi@chromium.org>
Date: Thu Nov 29 17:58:47 2018

Add last committed item URL validity check in SearchEngineTabHelper.

This CL adds a validity check for FaviconDriver::GetActiveURL().
GetActiveURL() depends on GetLastCommittedItem, and can be nil at various
times -- such as during session restore on startup.

Bug:  908240 
Change-Id: I32bcf8e93b862fd87ae22bce6c59cbb9c4ba2f5d
Reviewed-on: https://chromium-review.googlesource.com/c/1350873
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Commit-Queue: Yi Su <mrsuyi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612263}
[modify] https://crrev.com/1b6cda4e53ceec22638d07060bdb97008d97626e/ios/chrome/browser/search_engines/search_engine_tab_helper.mm

[Auto-generated comment by a script] We noticed that this issue is targeted for M-72; it appears the fix may have landed after branch point, meaning a merge might be required. Please confirm if a merge is required here - if so add Merge-Request-72 label, otherwise remove Merge-TBD label. Thanks.

mrsuyi: Does this CL need to be merged to M72? If so, please add merge-request-MXX label.

I think that this bug will only hit the DCHECK and won't cause a real crash, but the fix is quite simple so I guess it's worthy to merge it.

This bug requires manual review: Less than 18 days to go before AppStore submit on M72
Please contact the milestone owner if you have questions.
Owners: govind@(Android), kariahda@(iOS), djmm@(ChromeOS), abdulsyed@(Desktop)

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

So the risk in merging this is that we could crash more? Is that correct? How much more?

Why is it important that this makes M72?

I mean so far we don't have any report of crashes about this bug in dev&beta, and I've tested on simulators that this bug will only hit the DCHECK and won't really trigger a crash, so even if we don't merge it's 99% safe. Since the CL that fixed this bug is very simple and straight forward, if we merge it it's 100% safe.

Anyway, I think this CL has been inside M72 already, if this link is correct(https://chromiumdash.appspot.com/commit/1b6cda4e53ceec22638d07060bdb97008d97626e).

This is already in M72: https://storage.googleapis.com/chromium-find-releases-static/1b6.html#1b6cda4e53ceec22638d07060bdb97008d97626e. Removing merge request.