Fixed with CL :
https://chromium-review.googlesource.com/c/chromium/src/+/1075560

The new behavior is :

In presence of multiple infobars, download progress infobar will always show up at the bottom of the infobar stack.
Legal disclosure infobar (i.e. Search engine geolocation disclosure infobar) will always stay at the top.
Every other infobar stays in the middle in the order they are created (i.e. the newer infobar comes behind the older infobar)

Fix available in the next Canary. Please verify that it works.

Works as per expected new behavior as per C#2.  Tested on 69.0.3447.0

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

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/db28dfb2ed32dedd3ee71eaf9226bc56dd82123f

commit db28dfb2ed32dedd3ee71eaf9226bc56dd82123f
Author: Shakti Sahu <shaktisahu@chromium.org>
Date: Mon Jun 04 20:01:43 2018

Download infobar : Fix for conflict with duplicate download infobar

Currently infobars are added to the stack always at the back. So if
there is a new infobar coming up after download progress infobar,
it will get hidden behind it and if this new infobar is a confirm
infobar, user won't be able to take action. We can fix this issue
by treating download progress infobar as the lowest priority
(bottommost) infobar and always adding it to the bottom of the stack.

Bug:  847536 
Change-Id: Ie160d9bd1addf0ad90f6f2215a83c5e1c799c707
Reviewed-on: https://chromium-review.googlesource.com/1075560
Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#563321}(cherry picked from commit c5992300044af369e512a8831158db1676828bbc)
Reviewed-on: https://chromium-review.googlesource.com/1085970
Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/branch-heads/3440@{#162}
Cr-Branched-From: 010ddcfda246975d194964ccf20038ebbdec6084-refs/heads/master@{#561733}
[modify] https://crrev.com/db28dfb2ed32dedd3ee71eaf9226bc56dd82123f/chrome/android/java/src/org/chromium/chrome/browser/infobar/DownloadProgressInfoBar.java
[modify] https://crrev.com/db28dfb2ed32dedd3ee71eaf9226bc56dd82123f/chrome/android/java/src/org/chromium/chrome/browser/infobar/InfoBar.java
[modify] https://crrev.com/db28dfb2ed32dedd3ee71eaf9226bc56dd82123f/chrome/android/java/src/org/chromium/chrome/browser/infobar/InfoBarContainerLayout.java