Fix Google Play Music changes in HTML structure
Fix Google Play Music changes in HTML structure

Play music changed today from `sj-icon-button` elements to `paper-icon-button`.  This handles any *further* element changes.  We're still brittle against a data-id attribute change, but in this case, it's the most (only?) consistent thing short of using some logic to go hunting for the buttons.
miicha/browser-media-keys,miicha/browser-media-keys,gmelikov/browser-media-keys,gmelikov/browser-media-keys,gmelikov/browser-media-keys,carlin-q-scott/browser-media-keys,carlin-q-scott/browser-media-keys