Don't draw taskbar background during gestures

In this case, the ScrimView for BackgroundAppState will handle drawing behind the whole screen, and prevents taskbar from drawing the rounded corners on top of TaskViews.

Added a hack to defer resuming last task by a frame to ensure taskbar is drawing first.

Test: Quick switch to an app, ensure it isn't covered by the taskbar's rounded corner
Bug: 196257194
Change-Id: Ibc81d80bc3bf1d908e6912b179cbcafbdcc56c0f

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

@@ -23,6 +23,7 @@ import android.animation.AnimatorListenerAdapter;
 import android.animation.ObjectAnimator;
 import android.graphics.Rect;
 import android.view.MotionEvent;
+import android.view.View;
 
 import androidx.annotation.NonNull;
 
@@ -241,7 +242,11 @@ public class LauncherTaskbarUIController extends TaskbarUIController {
         return mContext.getDragController().isDragging();
     }
 
-    void setTaskbarViewVisible(boolean isVisible) {
+    public View getRootView() {
+        return mTaskbarDragLayer;
+    }
+
+    private void setTaskbarViewVisible(boolean isVisible) {
         mIconAlphaForHome.setValue(isVisible ? 1 : 0);
         mLauncher.getHotseat().setIconsAlpha(isVisible ? 0f : 1f);
     }