Also present on Mac, but estark reports that it doesn't repro on Linux (maybe IPC delay?)

Updating the ShowNotSecureWarning so that it doesn't call HidePopup() could affect cases where there was some other popup showing. 

That said, I couldn't find any way to trigger the password generator popup (even after turning it on in Chrome flags) and as of today, the only caller of the ShowHttpWarning is the "no creds stored" scenario, so the popup being hidden might always be the NotSecureWarning.

I think the "correct" fix would be to have a _is_showing_popup_a_not_secure_warning boolean or something similar, and just not call HidePopup if that's set already. (The HidePopup() call would clear the flag.)

Prototyping indicates that simply removing the HidePopup() call doesn't break anything.

https://codereview.chromium.org/2666873004

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3249c30a2d284c39241d2e7371656fe79c825669

commit 3249c30a2d284c39241d2e7371656fe79c825669
Author: elawrence <elawrence@chromium.org>
Date: Wed Feb 01 19:23:49 2017

Do not hide the "Login Not Secure" warning on keystrokes

The AutofillAgent::ShowNotSecureWarning function called HidePopup()
unnecessarily each time it was called. This caused the "Login Not
Secure" popup message to hide and reshow each time the user typed
a key.

Removing this call fixes the problem, and the code still behaves
correctly in the event that autofill suggestions are available or
the password generation popup is showing.

BUG= 685769 

TEST=From an empty profile, visit a HTTP page that collects passwords
(e.g. http://webdbg.com/test/forms/password.htm) and type in the name
or password fields. Observe the "Login Not Secure" warning message; it
should not flicker as characters are typed.

Review-Url: https://codereview.chromium.org/2666873004
Cr-Commit-Position: refs/heads/master@{#447575}

[modify] https://crrev.com/3249c30a2d284c39241d2e7371656fe79c825669/components/autofill/content/renderer/autofill_agent.cc

Fix is verified on Canary on Mac and Windows.

Your change meets the bar and is auto-approved for M57. Please go ahead and merge the CL to branch 2987 manually. Please contact milestone owner if you have questions.
Owners: amineer@(clank), cmasso@(bling), ketakid@(cros), govind@(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/+/c06f9992e3e6714a812d67b4cdb850d1bc99d567

commit c06f9992e3e6714a812d67b4cdb850d1bc99d567
Author: Emily Stark <estark@google.com>
Date: Fri Feb 03 18:49:12 2017

Do not hide the "Login Not Secure" warning on keystrokes

The AutofillAgent::ShowNotSecureWarning function called HidePopup()
unnecessarily each time it was called. This caused the "Login Not
Secure" popup message to hide and reshow each time the user typed
a key.

Removing this call fixes the problem, and the code still behaves
correctly in the event that autofill suggestions are available or
the password generation popup is showing.

BUG= 685769 

TEST=From an empty profile, visit a HTTP page that collects passwords
(e.g. http://webdbg.com/test/forms/password.htm) and type in the name
or password fields. Observe the "Login Not Secure" warning message; it
should not flicker as characters are typed.

Review-Url: https://codereview.chromium.org/2666873004
Cr-Commit-Position: refs/heads/master@{#447575}
(cherry picked from commit 3249c30a2d284c39241d2e7371656fe79c825669)

Review-Url: https://codereview.chromium.org/2672823005 .
Cr-Commit-Position: refs/branch-heads/2987@{#294}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}

[modify] https://crrev.com/c06f9992e3e6714a812d67b4cdb850d1bc99d567/components/autofill/content/renderer/autofill_agent.cc