Why won't my iphone 4s play music off of chrome/safari in the background?

Was it the 6.0.0- 6.1 update?
What i usually do is go to youtube on the chrome app and click play on a song.wait for the first second to play then press home. I then proceed to double tap home to get to my multitasking, slide over to the orientation lock/back-play-forword/app(usually music). I press play and it won't play the youtube video's sound in the background. It usually always does.
i've tried turning it on and off and deleting all my multitasking apps in background.

Added (1). If i have the video running, but i click the power button, then i double tap home at my lock screen, press play, it will work. It still doesn't work when the app closed/in background.

Added (2). Music app and soundcloud both work in backround.

Because that's not allowed anymore.

I don't think you can play sound from any other app in the background than the music app