Fixed a bug where a notification had no background

When tapping on a notification and then dragging down,
the notification had no background anymore

Bug: 16191184
Change-Id: I233a45744fc39ac3fcd9f533c8427354ab384709

packages/SystemUI/src/com/android/systemui/statusbar/ActivatableNotificationView.java

@@ -263,7 +263,9 @@ public abstract class ActivatableNotificationView extends ExpandableOutlineView
             animator.addListener(new AnimatorListenerAdapter() {
                 @Override
                 public void onAnimationEnd(Animator animation) {
-                    mBackgroundNormal.setVisibility(View.INVISIBLE);
+                    if (mDimmed) {
+                        mBackgroundNormal.setVisibility(View.INVISIBLE);
+                    }
                 }
             });
             animator.reverse();