ADDITIONAL COMMENT FROM SUBMITTER:
I've replicated this across two computers and user profiles on a brand-new installs of Windows in Hyper-V with minimal numbers of programs installed. Webroot antivirus is not monitoring the program or directory.

Please send my thanks to whoever put in the 100-attempt limit, it quickly downloads 1GB of these files and it would have consumed the disk otherwise.

ADDITIONAL COMMENT FROM SUBMITTER:
This is not a generic issue, Chrome successfully downloads and installs the uBlock origin extension. Sorry for not being clear.

+some Windows friends.

+rdevlin.cronin@, +benwells: do you have any guesses at the root cause of that message?

Oh dear...

This is because of a bug in content verification where we incorrectly marked these extensions as corrupted (see  issue 643814 ).  The bug has since been fixed, but it wasn't approved for M54 merge.

The fact that chrome is continually retrying to download the extension is based on the fact that since it's policy installed, there was concern around having relaxed limits or backoff, but I wonder if we need to tweak that...

Thanks everyone for the fast response. I did search the error message, but I guess I included too much.

I'm pulling our approval for HTTPS Everywhere from our group policy because we have hundreds of users on a pooled contract of tethered phone data for our laptops. Sorry I didn't submit this earlier, I thought it was just some obscure corner-case on a busted computer.

Actually the fix for  bug 643814  should be in chrome 54.0.2840.34 and higher (It was chrome 53 that we didn't merge it into). But there have still been some reports of problems, so maybe there's another bug we haven't found yet. 

Can you try running chrome with the policy setting to force install the extension, and follow the instructions I posted in comment 37 here:

https://bugs.chromium.org/p/chromium/issues/detail?id=643814#c37

and see if you see a request in the chrome://net-internals Events log for the verification data we need to fetch?

FYI, I've tried this in a test environment where I've either blocked or delayed the "installsource%3Dsignature" request using Fiddler, and if it is blocked then I see the behavior you describe, but if it is just delayed a reasonable amount things work out ok. Any chance you're running some other kind of extension that could be blocking certain requests?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6014bdfa1f211946627a7085c87fe922e1581fc5

commit 6014bdfa1f211946627a7085c87fe922e1581fc5
Author: asargent <asargent@chromium.org>
Date: Wed Nov 30 21:50:16 2016

Add throttling to corrupt policy extensions reinstall

For crbug.com/447040 (https://codereview.chromium.org/2299203004) we
made it so that enterprise policy force installed extensions would get
automatically reinstalled when we detected corruption. However, we
didn't add in any throttling, which was a bad idea because we turned out
to have a bug ( crbug.com/643814 ) where particular extensions were always
incorrectly detected as corrupt right after install. So at least one
enterprise with one of these extensions in their force install list
ended up having chrome spin in an loop redownloading/reinstalling one of
the affected extensions, eating up tons of bandwidth and disk space.

This CL adds in throttling with an exponentially backed off delay on
each reinstall attempt, up to a maximum of 30 minutes. The delay value
is only maintained in memory during the course of a single run of chrome
and resets after 6 hours (or on browser restart), but should be
sufficient to drastically reduce the problem reported for this bug.

BUG= 661738 

Review-Url: https://codereview.chromium.org/2533873003
Cr-Commit-Position: refs/heads/master@{#435430}

[modify] https://crrev.com/6014bdfa1f211946627a7085c87fe922e1581fc5/chrome/browser/extensions/chrome_content_verifier_delegate.cc
[modify] https://crrev.com/6014bdfa1f211946627a7085c87fe922e1581fc5/chrome/browser/extensions/chrome_content_verifier_delegate.h
[modify] https://crrev.com/6014bdfa1f211946627a7085c87fe922e1581fc5/chrome/browser/extensions/content_verifier_browsertest.cc

Should this be marked fixed, considering #11? Or at least downgraded from Pri1?

I think we can mark this as fixed.