Found an edge case that can happen with download location feature:

Repro steps:
1. Download somthing, the location dialog pops up.
2. Close browser.
3. Reopen browser, the snackbar shows. (The snackbar will only show once)

The reason is closing browser while location dialog showing will make download target file path to be empty and we don't handle that. The location dialog is part of target determination.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1bd7d9a35e9bf1e6b4a73e30a9f849ec32bf7dcd

commit 1bd7d9a35e9bf1e6b4a73e30a9f849ec32bf7dcd
Author: Xing Liu <xingliu@chromium.org>
Date: Tue Oct 02 21:25:59 2018

Download location: Missing SD card snackbar may show incorrectly.

This CL fixes an issue that missing SD card snackbar may show for users
without SD card.

The reason is the target path of the download can be empty if the user
kill the browser while download location dialog is showing.

Bug:  890867 
Change-Id: I2ed13acae1e4eface9703053506ef91b0b4d4110
Reviewed-on: https://chromium-review.googlesource.com/c/1257668
Commit-Queue: Xing Liu <xingliu@chromium.org>
Reviewed-by: Min Qin <qinmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595990}
[modify] https://crrev.com/1bd7d9a35e9bf1e6b4a73e30a9f849ec32bf7dcd/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java

This bug requires manual review: We are only 13 days from stable.
Please contact the 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

+benmason@ for merge review, thanks.

Approved for merge to 70, branch 3538.

Thanks!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/518b3934ad2dd2963da42c9bf7b2490bf97b31bd

commit 518b3934ad2dd2963da42c9bf7b2490bf97b31bd
Author: Xing Liu <xingliu@chromium.org>
Date: Thu Oct 04 18:26:32 2018

Download location: Missing SD card snackbar may show incorrectly.

This CL fixes an issue that missing SD card snackbar may show for users
without SD card.

The reason is the target path of the download can be empty if the user
kill the browser while download location dialog is showing.

TBR=xingliu@chromium.org

(cherry picked from commit 1bd7d9a35e9bf1e6b4a73e30a9f849ec32bf7dcd)

Bug:  890867 
Change-Id: I2ed13acae1e4eface9703053506ef91b0b4d4110
Reviewed-on: https://chromium-review.googlesource.com/c/1257668
Commit-Queue: Xing Liu <xingliu@chromium.org>
Reviewed-by: Min Qin <qinmin@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#595990}
Reviewed-on: https://chromium-review.googlesource.com/c/1262417
Reviewed-by: Xing Liu <xingliu@chromium.org>
Cr-Commit-Position: refs/branch-heads/3538@{#856}
Cr-Branched-From: 79f7c91a2b2a2932cd447fa6f865cb6662fa8fa6-refs/heads/master@{#587811}
[modify] https://crrev.com/518b3934ad2dd2963da42c9bf7b2490bf97b31bd/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java

The following revision refers to this bug: 
https://chromium.googlesource.com/chromium/src.git/+/518b3934ad2dd2963da42c9bf7b2490bf97b31bd

Commit: 518b3934ad2dd2963da42c9bf7b2490bf97b31bd
Author: xingliu@chromium.org
Commiter: xingliu@chromium.org
Date: 2018-10-04 18:26:32 +0000 UTC

Download location: Missing SD card snackbar may show incorrectly.

This CL fixes an issue that missing SD card snackbar may show for users
without SD card.

The reason is the target path of the download can be empty if the user
kill the browser while download location dialog is showing.

TBR=xingliu@chromium.org

(cherry picked from commit 1bd7d9a35e9bf1e6b4a73e30a9f849ec32bf7dcd)

Bug:  890867 
Change-Id: I2ed13acae1e4eface9703053506ef91b0b4d4110
Reviewed-on: https://chromium-review.googlesource.com/c/1257668
Commit-Queue: Xing Liu <xingliu@chromium.org>
Reviewed-by: Min Qin <qinmin@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#595990}
Reviewed-on: https://chromium-review.googlesource.com/c/1262417
Reviewed-by: Xing Liu <xingliu@chromium.org>
Cr-Commit-Position: refs/branch-heads/3538@{#856}
Cr-Branched-From: 79f7c91a2b2a2932cd447fa6f865cb6662fa8fa6-refs/heads/master@{#587811}

 Issue 774871  has been merged into this issue.