Enable 3 button nav for taskbar

Bug: 180046394
Test: Switched between gesture and button nav on
phone and tablet.

Change-Id: Iac2357a3256f8b6b36ca49d3680594a91e824a5f

quickstep/src/com/android/launcher3/taskbar/TaskbarKeyguardController.java

@@ -57,7 +57,7 @@ public class TaskbarKeyguardController {
         mKeyguardSysuiFlags = interestingKeyguardFlags;
 
         mBouncerShowing = bouncerShowing;
-        if (!mContext.canShowNavButtons()) {
+        if (!mContext.isThreeButtonNav()) {
             // For gesture nav we don't need to deal with bouncer or showing taskbar when locked
             return;
         }