Modified UI model objects to be backed merely by IDs of the core model objects.

Change-Id: I4ca81fb1c877ee4ce4209d405fd8c6645c8f5d20
diff --git a/core/api/src/main/java/org/onosproject/ui/model/topo/UiTopology.java b/core/api/src/main/java/org/onosproject/ui/model/topo/UiTopology.java
index 744c996..58e1b13 100644
--- a/core/api/src/main/java/org/onosproject/ui/model/topo/UiTopology.java
+++ b/core/api/src/main/java/org/onosproject/ui/model/topo/UiTopology.java
@@ -21,6 +21,7 @@
 import org.onosproject.net.HostId;
 import org.onosproject.net.PortNumber;
 import org.onosproject.net.region.RegionId;
+import org.onosproject.ui.model.ServiceBundle;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -72,6 +73,16 @@
     // a container for devices, hosts, etc. belonging to no region
     private final UiRegion nullRegion = new UiRegion(this, null);
 
+    final ServiceBundle services;
+
+    /**
+     * Creates a new UI topology backed by the specified service bundle.
+     *
+     * @param services service bundle
+     */
+    public UiTopology(ServiceBundle services) {
+        this.services = services;
+    }
 
     @Override
     public String toString() {