Turn on split from fullscreen with keyboard shortcuts flag

TODO: fix icon not showing in staged split view.

Bug: 261545797
Test: https://recall.googleplex.com/projects/f4cc906f-d337-414e-aea8-d5434a0c6e88/sessions/06cc05b5-c032-40f3-af8b-3b90860d2f37
Change-Id: I594b99afc2c282272a00608bb88c374aae36ab7d