Comment 38 for bug 248271

Agreed Ryan Hayle eye candy never should be done in expense of performance.

If you like tabs as much me, this problem is very obvious with newer PCs too. I have set browser.tabs.tabMinWidth to 34 and the tab close buttons are disabled. When I continue session with tab bar full of tabs or realod all tabs, the CPU usage will rise up to 100% and will stay there untill most of the tabs are loaded.

If I simply minimize the Firefox window or cover the tab bar with another window (throbbers are not drawn) while the tabs are loading the CPU usage drops near to ~10%

I wonder is Firefox renderin all the tab throbbers separately? The animation runs always at the same pace so Firefox could render the throbber just once and then draw the same throbber image on each tab, but then again I know nothing.