Yesterday I got crazy with a very special behavior of two of our iMacs (running with the latest Yosemite).
If you open a browser Tab in Safari or Chrome on the first iMac, it automatically opens in the task bar of the second one (Screenshot).
I disabled the Safari Cloud-Tabs Service in the iCloud, but the sharing keeps on going (still after rebooting, activating and deactivating again).
Funnily enough, it doesn't matter which browser you are using. Opening a tab in Safari displays it with a "chrome remote" icon on the other computer.
Has one of you ever seen this feature?
Both Macs are using the same iCloud-Address.
Btw: There is no Chrome "iCloud Tabs" Extension installed, but like I said this problem happens on Safari too.
Best Answer
If you really mean by automatically opens in task bar as a Browser icon displays a the little icon on top of it in the Dock (Handoff app icon in Dock ), and when you click it it opens the same page you are viewing on the other Mac.
then this is nothing to do with iCloud.
This a feature called Hand off. Have a read here