Dark color on super light wallpaper support

Change-Id: I0fdfa9abefb72e06c45b1f635ac97e2acfa97f05
diff --git a/res/layout-sw720dp/launcher.xml b/res/layout-sw720dp/launcher.xml
index b9b94b6..ca4d846 100644
--- a/res/layout-sw720dp/launcher.xml
+++ b/res/layout-sw720dp/launcher.xml
@@ -28,7 +28,7 @@
         android:clipChildren="false"
         android:clipToPadding="false"
         android:importantForAccessibility="no"
-        android:background="@drawable/workspace_bg"
+        android:background="?attr/workspaceStatusBarScrim"
         android:layout_width="match_parent"
         android:layout_height="match_parent">