Clear drag views during swipe up animation progress

This is to avoid clearing it too lately, at a point where the user starts to see a flicker on the screen.

There was already a report of this bug. Filing a bug report on my own because the original one is hard to find. I will mark that as fixed once I find it again.

Test: Manual
Fix: 259157574
Change-Id: Idc9bb67ebf6fc3ff6d78880f28c46d916a02ab77

quickstep/src/com/android/quickstep/AbsSwipeUpHandler.java

@@ -95,6 +95,7 @@ import com.android.launcher3.R;
 import com.android.launcher3.Utilities;
 import com.android.launcher3.anim.AnimationSuccessListener;
 import com.android.launcher3.anim.AnimatorPlaybackController;
+import com.android.launcher3.dragndrop.DragView;
 import com.android.launcher3.logging.StatsLogManager;
 import com.android.launcher3.logging.StatsLogManager.StatsLogger;
 import com.android.launcher3.statemanager.BaseState;
@@ -1363,6 +1364,10 @@ public abstract class AbsSwipeUpHandler<T extends StatefulActivity<S>,
         // If we are transitioning to launcher, then listen for the activity to be restarted while
         // the transition is in progress
         if (mGestureState.getEndTarget().isLauncher) {
+            // This is also called when the launcher is resumed, in order to clear the pending
+            // widgets that have yet to be configured.
+            DragView.removeAllViews(mActivity);
+
             TaskStackChangeListeners.getInstance().registerTaskStackListener(
                     mActivityRestartListener);