Open Radar

 
Summary:
When creating tabs or using the new Show All Tabs feature in 10.13's Terminal, the window shrinks by a few rows each time.

Steps to Reproduce:
1. Open a new Terminal window.
2. Press Command-I or otherwise turn on display of the Terminal's rows.
3. Press Command-T to open a new tab.
4. Observe the number of rows.
5. Press Command-Shift-\ repeatedly to toggle Show All Tabs. 
6. Observe the number of rows.

Expected Results:
1. The number of rows does not change.
2. Ideally if the window starts against the bottom edge of a screen, it would grow toward the top of the screen when adding a tab bar, to avoid the window displaying partially off the screen.

Actual Results:
1. The number of rows shrinks by a few when the tab bar shows.
2. The number of rows shrinks by a few for every invocation of Show All Tabs, until the terminal is 1 row high.
3. There are also several obvious cosmetic issues with Show All Tabs (e.g. the tab bar animation is not smooth, "popping" a few pixels at the end; title bar shading changes; window corners are squared off)

Version/Build:
Terminal 2.8/400

Configuration:
This is a regression from 10.12's Terminal (2.7.3/388.1.1) when displaying the tab bar; 10.12's Terminal did not have the Show All Tabs feature.

Attachments:
http://sabi.net/temp/34760016/shrinking%20Terminal.mov