Revert "[Overview Actions] UI update for Landscape."

This reverts commit 160ca4b8.

Reason for revert: Got issues like b/158318606 when switch nav modes, also the margin seems not set properly. And this doesn't work for 3 button mode too. Would switch to just use task menu for all.

Change-Id: I645f2a2a9032ae99799c75bcc6c983c1bbfd8df8