In 2D the tab switcher gets exited on the following signals:
1. The back button
2. Launching an external intent
3. Clicking the tab switcher button
4. Selecting a tab in the tab switcher
5. (Maybe others)

After crrev/c/1048269 lands we close for 4. 1. closes VR. 3. doesn't exist in VR yet. That leaves us with 2. and potential other signals not listed.

Define what to do for 2. and find other signals we should use for exiting the VR tabs overview. Implement solution accordingly.