PieChart: how to properly fix unreadable tooltip?

[Slava Semushin]

Hello,

I'm using Google Charts API v44 and I found something that looks like a bug. At the legend, when name of the entry is too long you can see a tooltip with this name. But in Firefox under Fedora it gets unreadable because the font color and background color are the same: https://cloud.githubusercontent.com/assets/87088/14206674/0d80ca76-f815-11e5-9a9b-a40fca7ef8af.png

I tried to customize the background color with backgroundColor property but it didn't work for me, I don't know why.. :-(

Then I decided to use CSS for that, like this: .goog-tooltip { color: white; } and it did the trick, but later I found out that now it got broken on my Mac: https://cloud.githubusercontent.com/assets/87088/14263541/674d73c6-fabb-11e5-8035-fb946b2b57bf.png

I want to ask a couple of questions regarding this:
1) how to customize font/background colors to make tooltips readable everywhere?
2) is this a bug in styles of google charts? I see that styles try to use colors from operation system but would it be better to use some default values to make
tooltips looks similar on all the browsers/OS?

Thanks in advance!