This question already has an answer here:
My friend bought a Sony Xperia Z3, and started to install all the apps she liked. After installing dozens of apps, she realized that there is a notification icon looks like a raindrop. I was asked to get rid of it, but I couldn’t. I tried to stop all the running apps, but it remained on top. If she pulls down the notification bar, it shows nothing.
Any idea what this could be?status