Merge changes from topic "taskbar-hotseat" into sc-dev

* changes:
  Update taskbar to add extra hotseat items instead of recent apps
  Add support for having more hotseat icons in the DB than we show

quickstep/src/com/android/launcher3/BaseQuickstepLauncher.java

@@ -108,6 +108,7 @@ public abstract class BaseQuickstepLauncher extends Launcher
         SysUINavigationMode.INSTANCE.get(this).removeModeChangeListener(this);
         if (mTaskbarController != null) {
             mTaskbarController.cleanup();
+            mTaskbarController = null;
         }
 
         super.onDestroy();