Password field changes height as you type in it

[Alan Pope 🍺🐧🐱 🦄]

Login to Ubuntu 17.10, lock screen.
On lock screen look at position of elements on screen
Start typing password

Expected behaviour

Screen elements stay in the same place, with password appearing in the password field

Actual behaviour

Password field grows vertically, causing everything above it to shift up, and everything below to shift down.

See screenshots of before/after, and comparison between the two images.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: gnome-shell 3.26.1-0ubuntu5
ProcVersionSignature: Ubuntu 4.13.0-17.20-generic 4.13.8
Uname: Linux 4.13.0-17-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.5
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Tue Dec 5 14:47:08 2017
DisplayManager: gdm3
GsettingsChanges:
 b'org.gnome.shell' b'command-history' b"['xkill', 'goxel']"
 b'org.gnome.shell' b'app-picker-view' b'uint32 1'
 b'org.gnome.shell' b'favorite-apps' b"['org.gnome.Nautilus.desktop', 'org.gnome.Software.desktop', 'google-chrome.desktop', 'chrome-hebeiaianhihkafkbopcfpkgloimgagb-Default.desktop', 'discord.desktop', 'chrome-flidaonfhnkbealpaagddgffpppelhhb-Profile_1.desktop', 'chrome-celnaknmndcdcjcagffhbhciignkeokb-Default.desktop', 'chrome-dcdbodpaldbchkfinnjphocleggfceip-Default.desktop', 'chrome-ddiddklncfgbfaaahngklemobghhjkim-Default.desktop', 'chrome-fimghoffjcofmboofohmacdeabiimdeg-Profile_1.desktop', 'irccloud-desktop_irccloud-desktop.desktop', 'telegramdesktop.desktop', 'org.gnome.Terminal.desktop', 'code.desktop']"
 b'org.gnome.desktop.interface' b'gtk-im-module' b"'gtk-im-context-simple'"
InstallationDate: Installed on 2017-08-02 (124 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Alpha amd64 (20170712)
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Daniel van Vugt (vanvugt)]

Confirmed. But I wonder if this is specific to ubuntu-themes?

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[AsciiWolf (asciiwolf)]

@vanvugt: It does not happen when using the default Adwaita theme.

[AsciiWolf (asciiwolf)]

Still not fixed. :-(