You are probably looking for a change made after 513963(known good), but no later than 513964(first known bad).
CHANGELOG URL:
The script might not always return single CL as suspect as some perf builds might get missing due to failure.

https://chromium.googlesource.com/chromium/src/+log/d5870fde3b3179c29ed7ff1741de1e130392f7e0..d12aa0cfc5a466ab51f6d1ee866821a0c42b1cf5

Suspect: https://chromium.googlesource.com/chromium/src/+/d12aa0cfc5a466ab51f6d1ee866821a0c42b1cf5

Adding release blocker for this issue.Please undo if not the case.

Thank you!

Another repro (duplicate issue):
1. open NTP
2. open chrome://extensions
3. click Details on an extension
4. change the URL to a bogus extension ID (to simulate asking for details on a non-existent URL)
5. Click back as much as ya like.
Problem: doesn't reach NTP again.

Another repro (similar to #7)
1. from any page
2. navigate to chrome://extensions/?id=xxxxxxxxxxxxxxxxxxxxxx
5. Click back as much as ya like.
Problem: doesn't reach original page again.

So IIUC, the problem is somewhere within the logic of the navigation listener at [1]?

cc'ing Scott who might have some good insight.

[1] https://cs.chromium.org/chromium/src/chrome/browser/resources/md_extensions/manager.js?sq=package:chromium&dr&l=183

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4e931006d1a302678a22a9498db1e04e78860510

commit 4e931006d1a302678a22a9498db1e04e78860510
Author: Dave Schuyler <dschuyler@chromium.org>
Date: Mon Dec 04 22:11:41 2017

[MD extensions] clear removed extension id url from history

This CL fixes an issue with the page history. If an extension is removed
and the user tries to navigate back to the details page for that
extension, they may get caught in a loop (unable to go back). This CL
will navigate back or replace the history element (there are two different
cases: removing an extension from the details page; or navigating to an
invalid extension ID).

FYI, the case where the extension is removed from the main list page is
not affected (it doesn't have the issue).

Bug:  789891 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I45eb0f2917452da55e0e07c67356e24ae5bd56bb
Reviewed-on: https://chromium-review.googlesource.com/801975
Commit-Queue: Dave Schuyler <dschuyler@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521483}
[modify] https://crrev.com/4e931006d1a302678a22a9498db1e04e78860510/chrome/browser/resources/md_extensions/manager.js
[modify] https://crrev.com/4e931006d1a302678a22a9498db1e04e78860510/chrome/browser/resources/md_extensions/navigation_helper.js
[modify] https://crrev.com/4e931006d1a302678a22a9498db1e04e78860510/chrome/test/data/webui/extensions/extension_manager_unit_test.js
[modify] https://crrev.com/4e931006d1a302678a22a9498db1e04e78860510/chrome/test/data/webui/extensions/extension_navigation_helper_test.js

I've verified this fix is in ToT.

Approving merge to M64 Chrome OS.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ea7f1beaa44c73a187665dc17050856706589452

commit ea7f1beaa44c73a187665dc17050856706589452
Author: Dave Schuyler <dschuyler@chromium.org>
Date: Wed Dec 06 20:04:00 2017

[MD extensions] clear removed extension id url from history

This CL fixes an issue with the page history. If an extension is removed
and the user tries to navigate back to the details page for that
extension, they may get caught in a loop (unable to go back). This CL
will navigate back or replace the history element (there are two different
cases: removing an extension from the details page; or navigating to an
invalid extension ID).

FYI, the case where the extension is removed from the main list page is
not affected (it doesn't have the issue).

Bug:  789891 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I45eb0f2917452da55e0e07c67356e24ae5bd56bb
Reviewed-on: https://chromium-review.googlesource.com/801975
Commit-Queue: Dave Schuyler <dschuyler@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#521483}(cherry picked from commit 4e931006d1a302678a22a9498db1e04e78860510)
Reviewed-on: https://chromium-review.googlesource.com/811904
Reviewed-by: Dave Schuyler <dschuyler@chromium.org>
Cr-Commit-Position: refs/branch-heads/3282@{#65}
Cr-Branched-From: 5fdc0fab22ce7efd32532ee989b223fa12f8171e-refs/heads/master@{#520840}
[modify] https://crrev.com/ea7f1beaa44c73a187665dc17050856706589452/chrome/browser/resources/md_extensions/manager.js
[modify] https://crrev.com/ea7f1beaa44c73a187665dc17050856706589452/chrome/browser/resources/md_extensions/navigation_helper.js
[modify] https://crrev.com/ea7f1beaa44c73a187665dc17050856706589452/chrome/test/data/webui/extensions/extension_manager_unit_test.js
[modify] https://crrev.com/ea7f1beaa44c73a187665dc17050856706589452/chrome/test/data/webui/extensions/extension_navigation_helper_test.js