ONOS-6258: UiTopo2Overlay et al.
- revert DriverMatrix app.
- simplify overlay base class to be consistent with classic topo
- add topo2overlay and topo2traffic (skeleton code for now)

Change-Id: I88fda4d7b75807bd08637d846a869846a364c1f8
diff --git a/web/gui/src/main/java/org/onosproject/ui/impl/topo/Topo2OverlayCache.java b/web/gui/src/main/java/org/onosproject/ui/impl/topo/Topo2OverlayCache.java
index 1c05acf..b95aeaf 100644
--- a/web/gui/src/main/java/org/onosproject/ui/impl/topo/Topo2OverlayCache.java
+++ b/web/gui/src/main/java/org/onosproject/ui/impl/topo/Topo2OverlayCache.java
@@ -135,12 +135,7 @@
     // overlay instance representing "no overlay selected"
     private static class NullOverlay extends UiTopo2Overlay {
         NullOverlay() {
-            super(EMPTY, NO_OVERLAY);
-        }
-
-        @Override
-        public String glyphId() {
-            return UNKNOWN;
+            super(EMPTY);
         }
     }
 }