TopoRegions: created skeleton Topo2 UI view for development of the "region-aware" topology.
 - Added initial event generation (layout/region/ etc.) -- WIP

Change-Id: I2f93eea7505ff0400085d7f67491f6b61231cb86
diff --git a/web/gui/src/main/java/org/onosproject/ui/impl/topo/model/ModelCache.java b/web/gui/src/main/java/org/onosproject/ui/impl/topo/model/ModelCache.java
index 6566511..8754550 100644
--- a/web/gui/src/main/java/org/onosproject/ui/impl/topo/model/ModelCache.java
+++ b/web/gui/src/main/java/org/onosproject/ui/impl/topo/model/ModelCache.java
@@ -41,6 +41,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.util.List;
 import java.util.Set;
 
 import static org.onosproject.net.DefaultEdgeLink.createEdgeLink;
@@ -153,6 +154,10 @@
         }
     }
 
+    List<UiClusterMember> getAllClusterMembers() {
+        return uiTopology.allClusterMembers();
+    }
+
 
     // === MASTERSHIP CHANGES
 
@@ -199,7 +204,7 @@
 
     // package private for unit test access
     UiRegion accessRegion(RegionId id) {
-        return uiTopology.findRegion(id);
+        return id == null ? null : uiTopology.findRegion(id);
     }
 
     // invoked from UiSharedTopologyModel region listener
@@ -484,4 +489,5 @@
     public int hostCount() {
         return uiTopology.hostCount();
     }
+
 }