Slightly off-topic, but since the 'UI' is in the topic, I'll bite:
Why did Google need to re-invent the scrollbar ( http://i.imgur.com/ztm93.png ), without the two squares (sorry, don't know what they're called) on the opposite sides, which you can click without having to move the mouse up/down;left/right?
What is wrong with traditional scrollbars that Google felt the need to get away from it?
Unfortunately some influential sites and UI designers have lately been trying to improve on the standard scrollbar [1], often in an attempt to make them work better for very small screens and/or touchscreen devices. IMHO, their changes have mostly been steps backwards as far as traditional mousing is concerned. The scrollbar is old and highly evolved. It's not immediately obvious that it can be improved. I suspect it will be with us until we eliminate scrolling itself.
In Firefox and Opera, the arrow buttons are showing up fine for me. How are you viewing this?
Probably because the "squares" have a very small target area and most people either use the scroll button if they're using a mouse or scroll gestures if they're using a touchpad. I'm pretty sure they have detailed information about this from the metrics that they collect from Chrome.
Why did Google need to re-invent the scrollbar ( http://i.imgur.com/ztm93.png ), without the two squares (sorry, don't know what they're called) on the opposite sides, which you can click without having to move the mouse up/down;left/right?
What is wrong with traditional scrollbars that Google felt the need to get away from it?