Not obvious if enabling this feature caused the test flake. Assigning to CL author for further investigation.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e6bd9834dd435d4d163c18b6582ef8d859c94e8f

commit e6bd9834dd435d4d163c18b6582ef8d859c94e8f
Author: Bailey Berro <baileyberro@chromium.org>
Date: Thu Sep 06 01:03:11 2018

Do not modify SmbService or SmbFileSystem on non-UI thread

- Previously SmbService and SmbFileSystem initialized their
temp_file_manager_ members via a Task which was run on a non-UI thread.
Changes to the class state should only happen on the UI thread to avoid
race conditions.

Bug:  879911 
Change-Id: If79b0cd1162d2080c9ec1d44b0beb62cc53e8278
Reviewed-on: https://chromium-review.googlesource.com/1208193
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Commit-Queue: Bailey Berro <baileyberro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589077}
[modify] https://crrev.com/e6bd9834dd435d4d163c18b6582ef8d859c94e8f/chrome/browser/chromeos/smb_client/smb_file_system.cc
[modify] https://crrev.com/e6bd9834dd435d4d163c18b6582ef8d859c94e8f/chrome/browser/chromeos/smb_client/smb_file_system.h
[modify] https://crrev.com/e6bd9834dd435d4d163c18b6582ef8d859c94e8f/chrome/browser/chromeos/smb_client/smb_service.cc
[modify] https://crrev.com/e6bd9834dd435d4d163c18b6582ef8d859c94e8f/chrome/browser/chromeos/smb_client/smb_service.h

This should be fixed, is there a way to use FindIt to confirm the flake is gone?

Requesting the CL above be merged to 70.

Enabling our feature made this test flakey, so this fixes the test flake.

Your change meets the bar and is auto-approved for M70. Please go ahead and merge the CL to branch 3538 manually. Please contact milestone owner if you have questions.
Owners: benmason@(Android), kariahda@(iOS), geohsu@(ChromeOS), abdulsyed@(Desktop)

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

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0d1337cc80eea29bb5c0b06abc607c75697c2885

commit 0d1337cc80eea29bb5c0b06abc607c75697c2885
Author: Bailey Berro <baileyberro@chromium.org>
Date: Mon Sep 10 14:20:38 2018

Do not modify SmbService or SmbFileSystem on non-UI thread

- Previously SmbService and SmbFileSystem initialized their
temp_file_manager_ members via a Task which was run on a non-UI thread.
Changes to the class state should only happen on the UI thread to avoid
race conditions.

Bug:  879911 
Change-Id: If79b0cd1162d2080c9ec1d44b0beb62cc53e8278
Reviewed-on: https://chromium-review.googlesource.com/1208193
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Commit-Queue: Bailey Berro <baileyberro@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#589077}(cherry picked from commit e6bd9834dd435d4d163c18b6582ef8d859c94e8f)
Reviewed-on: https://chromium-review.googlesource.com/1216031
Cr-Commit-Position: refs/branch-heads/3538@{#208}
Cr-Branched-From: 79f7c91a2b2a2932cd447fa6f865cb6662fa8fa6-refs/heads/master@{#587811}
[modify] https://crrev.com/0d1337cc80eea29bb5c0b06abc607c75697c2885/chrome/browser/chromeos/smb_client/smb_file_system.cc
[modify] https://crrev.com/0d1337cc80eea29bb5c0b06abc607c75697c2885/chrome/browser/chromeos/smb_client/smb_file_system.h
[modify] https://crrev.com/0d1337cc80eea29bb5c0b06abc607c75697c2885/chrome/browser/chromeos/smb_client/smb_service.cc
[modify] https://crrev.com/0d1337cc80eea29bb5c0b06abc607c75697c2885/chrome/browser/chromeos/smb_client/smb_service.h