Official Google Play Music app for Chrome can now be used without having to open the Play Music site in a new tab. Simply run the mini player by clicking on "I'm feeling lucky radio" and then you can close all the Chrome tabs.
The mini player also supports keyboard shortcuts:
* left arrow - previous song
* right arrow - next song
* down arrow - decrease volume
* up arrow - increase volume
* p / space bar - pause/play music
* r - toggle repeat between off, all, and one
* s - toggle shuffle on or off
* = - thumbs up