The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3ee963d4e6487ff95572bc5929e08ef797e71df8

commit 3ee963d4e6487ff95572bc5929e08ef797e71df8
Author: Shakti Sahu <shaktisahu@chromium.org>
Date: Wed May 30 17:51:22 2018

Download infobar : Fixed bug where infobar disappears after a while

This happens due to the TabModelSelector cached by the controller getting
overwritten any time when we open a CustomTabActivity. This also doesn't
work in multi-window mode. Using the last focused activity gives us
better control of the situation in this case. Though it doesnot solve
multi-window scenario completely (as we may need to have one controller
for each activity), it is definitely better than using tab model selector.

Bug:  847534 
Change-Id: Ieca2c82adea89ee55894284b0eab10fc9068492d
Reviewed-on: https://chromium-review.googlesource.com/1074450
Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#562902}
[modify] https://crrev.com/3ee963d4e6487ff95572bc5929e08ef797e71df8/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
[modify] https://crrev.com/3ee963d4e6487ff95572bc5929e08ef797e71df8/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadInfoBarController.java
[modify] https://crrev.com/3ee963d4e6487ff95572bc5929e08ef797e71df8/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java

[Auto-generated comment by a script] We noticed that this issue is targeted for M-68; it appears the fix may have landed after branch point, meaning a merge might be required. Please confirm if a merge is required here - if so add Merge-Request-68 label, otherwise remove Merge-TBD label. Thanks.

Your change meets the bar and is auto-approved for M68. Please go ahead and merge the CL to branch 3440 manually. Please contact milestone owner if you have questions.
Owners: cmasso@(Android), kariahda@(iOS), bhthompson@(ChromeOS), abdulsyed@(Desktop)

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

This happens when you click open for the completed download.

Fixed in canary.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3a6e961c756c8607f16310be5c5c2abcee526305

commit 3a6e961c756c8607f16310be5c5c2abcee526305
Author: Shakti Sahu <shaktisahu@chromium.org>
Date: Fri Jun 01 00:33:17 2018

Download infobar : Fixed bug where infobar disappears after a while

This happens due to the TabModelSelector cached by the controller getting
overwritten any time when we open a CustomTabActivity. This also doesn't
work in multi-window mode. Using the last focused activity gives us
better control of the situation in this case. Though it doesnot solve
multi-window scenario completely (as we may need to have one controller
for each activity), it is definitely better than using tab model selector.

TBR=shaktisahu@chromium.org

(cherry picked from commit 3ee963d4e6487ff95572bc5929e08ef797e71df8)

Bug:  847534 
Change-Id: Ieca2c82adea89ee55894284b0eab10fc9068492d
Reviewed-on: https://chromium-review.googlesource.com/1074450
Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#562902}
Reviewed-on: https://chromium-review.googlesource.com/1081681
Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/branch-heads/3440@{#78}
Cr-Branched-From: 010ddcfda246975d194964ccf20038ebbdec6084-refs/heads/master@{#561733}
[modify] https://crrev.com/3a6e961c756c8607f16310be5c5c2abcee526305/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
[modify] https://crrev.com/3a6e961c756c8607f16310be5c5c2abcee526305/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadInfoBarController.java
[modify] https://crrev.com/3a6e961c756c8607f16310be5c5c2abcee526305/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java

Verified in 69.0.3452.0 build