Add new buttons to taskbar

Cherry picked from commit 53db50dd0b2bd6ed1842b25396c9c52b7abe1157
after resolving conflicts

The CL adds two new buttons for desktop usage.
No listeners are registered yet.

Recall: http://recall/clips/f52b70ed-c437-4374-a492-e4b7c802520a

Bug: 198355239
Test: m, verify that new buttons are added

Change-Id: I1d4a12da3041e113a978c37c9e36ec085d15e8b3