Add some little contrast or border for balloon tooltips

[lemon-juice]

First of all thanks for the great theme, so far I like it a lot and with a few tweaks in the Color Scheme settings I've been able to make an almost perfect theme that suits my taste. I use it in PHPStorm. However, there are some small problems that I can't change through the Color Scheme settings - balloon tooltips have the same background as the editor and no borders, which sometimes makes it hard to distinguish where they are because they can visually blend with other content.

One such example is argument info when you press Ctrl+P on a function/method argument:

Other examples are info balloons from the IDE for events like finished file upload or updates info:

Could you make some distinction for these tooltip layers so their boundaries are more visible? They don't have to be in high contrast but anything visually discernible. For example, function documentation (Ctrl+Q) looks very well: