Unusual Dock Icon Appearing in OS X 10.10 Yosemite
That is Handoff and a natural feature when OS X and iOS devices are signed into the same iCloud account. This works if you have iOS 8+ or OS X 10.10.x Yosemite. If you have a supported application then you will be able to open it on your Mac right where you left off on your iOS device.

Looks like you was running Chrome on your iPad at the time.

If you wish to disable Handoff on a Mac, open 'System Preferences' and select 'General'. It's the check box labeled "Allow Handoff..." towards the bottom of the window pane.

If Bluetooth is off, Handoff is disabled as well.