It certainly seemed unlikely there for a while, but now it’s almost undeniable: Chris Brown has managed to bounce back from his abuse of ex-girlfriend Rihanna and is well on his way to reestablishing himself as the reigning young R&B heartthrob. The way back to the summit hasn’t always been smooth, but — thanks in large part to current hit “Deuces” and its star-studded remix — it has been surprisingly swift. Now sure to accelerate the process: Over the weekend, Brown tweeted that he and Justin Bieber are collaborating on a single. Brown writes: “ME and @justinbieber got a BANGER/SMASH record for all the fans out there at the top of the NEW YEAR!!! 2011.” Bieber has been carefully cultivating a variety of demographics for his next album; he recently announced a duet with pop-country superstars Rascal Flatts. But this collaboration feels a bit more organic — not only is Bieber actually nestled right into the age demographic that’s young enough to already see Chris Brown as a historically major pop music figure, but it turns out that a pre-fame Bieber covered CB on his YouTube page. That means you can understand why Justin would want to provide Brown with this kind of major assist, despite the baggage involved. Anyway: It may not please everyone, but Chris Brown’s public image is halfway rehabilitated.