Restore divider between app predictions and apps

Screenshot: https://screenshot.googleplex.com/89jJLU3JXV8tRXM
Bug: 180017741
Test: Manual
Change-Id: Iab1764fe94340f120770054cf5a59bd3ed9e45a4

src/com/android/launcher3/allapps/FloatingHeaderRow.java

@@ -61,4 +61,11 @@ public interface FloatingHeaderRow {
      * Returns a child that has focus to be launched by the IME.
      */
     View getFocusedChild();
+
+    /**
+     * Returns true if view is currently visible
+     */
+    default boolean isVisible() {
+        return shouldDraw();
+    }
 }