Bug 1043712 - Music app fast forward

When the user try to switch to next/previous songs, then it's okay to handle the next/previous buttons in the click case. But when the user try to long tap the next/previous buttons to trigger the fast forward/rewind, we will receive the click event as well, so that means after the user's finger leaves the panel, besides the contextmenu event, the click event will also fire then trigger the next()/previous().