Add support for popup dark theme

Bug: 62380473
Change-Id: Ib22e9b82841bf10b7f139638f268f0a878e3c6b9
diff --git a/res/layout/notification_footer.xml b/res/layout/notification_footer.xml
index ed2212b..86280e0 100644
--- a/res/layout/notification_footer.xml
+++ b/res/layout/notification_footer.xml
@@ -22,7 +22,7 @@
     android:elevation="@dimen/notification_elevation"
     android:clipChildren="false"
     android:layout_gravity="center_vertical"
-    android:background="@color/popup_background_color">
+    android:background="?attr/popupColorPrimary">
 
     <LinearLayout
         android:id="@+id/icon_row"