ComboBoxButton shrinks as locale is changed.

[pixelzoom]

This is a (new?) problem with ComboBox, and I'm seeing it in all sims. As locale is changed, the ComboBoxButton gets progressively smaller. I'm seeing this in main with balancing-chemical-equations, beers-law-lab, geometric-optics, ph-scale, ...

To demonstrate in balancing-chemical-equations:

1. From phetmarks, run http://localhost:8080/balancing-chemical-equations/balancing-chemical-equations_en.html?brand=phet&ea&debugger&locales=*
2. Got to the Intro screen.
3. Open Preferences > Localization. Note the size of the Tools combobox in the upper-right corner of the screen:

5. Select each Locale in order, starting from "Afaan Oromoo". Note that the ComboBoxButton gets progressively smaller. By the time you select "English" from the Localization tab, the combobox will look like this:


6. Keep selecting locales and the ComboBoxButton will continue to get smaller:

[jonathanolson]

Fixed in the commit above. @pixelzoom can you verify?

[marlitas]

I confirmed this is now working on the local version of MSaB.

[samreid]

@marlitas confirmed it does not need a maintenance release. @marlitas reviewed the proposed solution and it seems good.

[pixelzoom]

Tested in BCE and this appears to be fixed in main.

Comments above indicate that an MR is needed, so assigning to @jonathanolson.