qnnguyen@ if you have time feel free to polish the behavior here more, but likely we need to look at this more comprehensively to get good behavior. Post-m70 should be okay for this.

jdufault@ Sure. This change was made quite intentionally. If you recall, I updated the layout code for the bubbles to make sure that they don't extend into the shelf area, and if they do, we just bump the bubble up so it doesn't anymore.

I think the main issue is that I don't really have a clear understanding of what the correct behavior *should* be. You could imagine a case with a slightly smaller screen, where if we didn't obscure the password field, we would end up cutting off some of the label text at the bottom instead. As an aside, I've noticed that webui login doesn't really handle this super gracefully either (it seems to bunch up the text on top of itself if it's about to go off the bottom). So it seems that this edge case hasn't been fully handled yet.

Indeed, I think we need to consider the various edge cases and discuss with UX on the best possible solution.

FYI, web-ui login didn't really have this issue because the texts in the error bubble has smaller letter spacing, thus the bubble size is much smaller and it doesn't expand to the shelf area on smaller devices such as Paine.

I didn't find the letter spacing value in the spec for the error bubble. It seems that web-ui and views lock has used different values each.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/593f022c3388819e053d6426dda7f4d84d62145d

commit 593f022c3388819e053d6426dda7f4d84d62145d
Author: Quan Nguyen <qnnguyen@chromium.org>
Date: Mon Sep 10 22:15:12 2018

cros: Don't reposition login bubbles vertically.

Previously we prevented the login bubbles from overlapping into the shelf.
This had some annoying side effects like obscuring the password field. This
CL removes that part of the widget repositioning logic.

A future CL will address the potential case of login bubbles going off screen
on the bottom. Need to clarify the correct UX for this case.

Bug:  880224 ,  875787 
Change-Id: Iea42cd612e9b0c57516fdc9681843182fa8d268b
Reviewed-on: https://chromium-review.googlesource.com/1217742
Reviewed-by: Jacob Dufault <jdufault@chromium.org>
Commit-Queue: Quan Nguyen <qnnguyen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590087}
[modify] https://crrev.com/593f022c3388819e053d6426dda7f4d84d62145d/ash/login/ui/login_bubble.cc
[modify] https://crrev.com/593f022c3388819e053d6426dda7f4d84d62145d/ash/login/ui/login_bubble.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1736d324df7607dfb737daeff789ff7fc2c8b687

commit 1736d324df7607dfb737daeff789ff7fc2c8b687
Author: Quan Nguyen <qnnguyen@chromium.org>
Date: Wed Sep 12 22:46:55 2018

cros: Don't reposition login bubbles vertically.

Previously we prevented the login bubbles from overlapping into the shelf.
This had some annoying side effects like obscuring the password field. This
CL removes that part of the widget repositioning logic.

A future CL will address the potential case of login bubbles going off screen
on the bottom. Need to clarify the correct UX for this case.

Bug:  880224 ,  875787 
Change-Id: Iea42cd612e9b0c57516fdc9681843182fa8d268b
Reviewed-on: https://chromium-review.googlesource.com/1217742
Reviewed-by: Jacob Dufault <jdufault@chromium.org>
Commit-Queue: Quan Nguyen <qnnguyen@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#590087}(cherry picked from commit 593f022c3388819e053d6426dda7f4d84d62145d)
Reviewed-on: https://chromium-review.googlesource.com/1222747
Cr-Commit-Position: refs/branch-heads/3538@{#346}
Cr-Branched-From: 79f7c91a2b2a2932cd447fa6f865cb6662fa8fa6-refs/heads/master@{#587811}
[modify] https://crrev.com/1736d324df7607dfb737daeff789ff7fc2c8b687/ash/login/ui/login_bubble.cc
[modify] https://crrev.com/1736d324df7607dfb737daeff789ff7fc2c8b687/ash/login/ui/login_bubble.h