Support blacklisting live wallpapers from showing sysui scrims

Add wallpaper changed broadcast receiver to BaseDragLayer, which
checks if the new wallpaper is blacklisted and relays that to
remove the scrims.

Bug: 150144115
Change-Id: I55b7b98fdd419cd76532492461a872367efed67b
diff --git a/res/values/config.xml b/res/values/config.xml
index 6c239bd..1675a98 100644
--- a/res/values/config.xml
+++ b/res/values/config.xml
@@ -176,4 +176,7 @@
         <item>@dimen/swipe_up_fling_min_visible_change</item>
         <item>@dimen/swipe_up_y_overshoot</item>
     </array>
+
+    <string-array name="live_wallpapers_remove_sysui_scrims">
+    </string-array>
 </resources>