Fix cast exception when dropping widgets to a drop target

When inflating a widget directly in the DragView, I've overridden
the layout param to FrameLayout.LayoutParam. Before drag complete,
we should restore the previous layout param.

Test: Drag a widget to a drop target. No crash is observed.
Bug: 186111130
Change-Id: Ifd33d57a886496ab31d4e741870b0ae18ca9ce4e

src/com/android/launcher3/ButtonDropTarget.java

@@ -240,6 +240,7 @@ public abstract class ButtonDropTarget extends TextView
 
         final Rect to = getIconRect(d);
         final float scale = (float) to.width() / from.width();
+        d.dragView.detachContentView(/* reattachToPreviousParent= */ true);
         mDropTargetBar.deferOnDragEnd();
 
         Runnable onAnimationEndRunnable = () -> {