Different profiles are using the same path for storing the copy of the local image: https://cs.chromium.org/chromium/src/chrome/browser/search/instant_service.cc?l=88.

Needs to be stored in the profile directory instead.

One other thing I'm noticing is not necessarily due to profile sharing / overwriting, but potentially cache expiry. A background image set on Friday (background.jpg?ts=1537570958) is no longer loading today. The file doesn't exist at /usr/local/google/home/ramyan/.config/google-chrome/.

I think Yana's issue was similar - when reported, it was 48hr+ past the ts encoded in the background URL.

I'll try to repro on a machine where there's only one profile.

The file shouldn't be removed unless you change/reset the background

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ed7c3b311e22e62f62b2c9c9b414255b048423dc

commit ed7c3b311e22e62f62b2c9c9b414255b048423dc
Author: Kyle Milka <kmilka@chromium.org>
Date: Tue Sep 25 16:24:16 2018

[NTP] Use profile path for local image copy

Previously the local image copy was stored in the user data directory
meaning that all profiles shared a single image. Instead each profile
should have a separate copy.

Bug:  888076 
Change-Id: I91c052fa7d440b1adeb5d98cd8bfc35a37d976aa
Reviewed-on: https://chromium-review.googlesource.com/1239456
Commit-Queue: Kyle Milka <kmilka@chromium.org>
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593960}
[modify] https://crrev.com/ed7c3b311e22e62f62b2c9c9b414255b048423dc/chrome/browser/search/instant_service.cc
[modify] https://crrev.com/ed7c3b311e22e62f62b2c9c9b414255b048423dc/chrome/browser/search/instant_service_unittest.cc
[modify] https://crrev.com/ed7c3b311e22e62f62b2c9c9b414255b048423dc/chrome/browser/search/local_ntp_source.cc

Following up on c#3: I attempted to repro on a fresh install (on Windows) with a single profile. Uploaded the image ~72 hours ago & it's still shown as the NTP background. 

So it looks like just the single issue (sharing across profiles) that was the cause of this. 

Also see  issue 889571 , which may turn out to be a dupe of this.

Closing this, since it looks to be all fixed now

Issue 896760 has been merged into this issue.