"Expand Sidebar" button shifts slightly and when sidebar is toggled

[Pyroglyph]

Captchas

• I have read the instructions.
• I have searched existing issues and avoided creating duplicates.
• I am not filing an enhancement request.
• I have checked that this issue cannot be reproduced on Mozilla Firefox.
• I have checked that this issue can be reproduced once I removed all my Mods and Custom CSS.

What happened?

What happened:
When toggling the expanded state of the sidebar (either clicking the Expand Sidebar button or using a keyboard shortcut), the button becomes vertically misaligned when the sidebar is collapsed, and slightly horizontally misaligned when expanded.

The black lines were added to highlight the misalignment.

I have also noticed the button itself seems to get bigger when in the collapsed state (shown by the rounded square that appears when you hover over it, not pictured)

What I expected:
The button should stay aligned, as it does in Firefox.

Version

1.11.4b

What platform are you seeing the problem on?

Linux (Tarball)

What component is this issue related to?

Tabs

Relevant log output if applicable

[sporocyst]

I don't thick the top icons shoud be aligned with tab icon when sidebar is expanded.

[Pyroglyph]

I don't thick the top icons shoud be aligned with tab icon when sidebar is expanded.

While we may disagree on what the button should be aligned with, I'm sure we can agree that the button moving is a bug:

[sporocyst]

You are right on that it can be more polished