Added getDeviceCount and tests.
diff --git a/net/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceManager.java b/net/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceManager.java
index 9986b0d..b8f5788 100644
--- a/net/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceManager.java
+++ b/net/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceManager.java
@@ -69,9 +69,8 @@
     }
 
     @Override
-    public MastershipRole getRole(DeviceId deviceId) {
-        checkNotNull(deviceId, DEVICE_ID_NULL);
-        return store.getRole(deviceId);
+    public int getDeviceCount() {
+        return store.getDeviceCount();
     }
 
     @Override
@@ -86,6 +85,12 @@
     }
 
     @Override
+    public MastershipRole getRole(DeviceId deviceId) {
+        checkNotNull(deviceId, DEVICE_ID_NULL);
+        return store.getRole(deviceId);
+    }
+
+    @Override
     public List<Port> getPorts(DeviceId deviceId) {
         checkNotNull(deviceId, DEVICE_ID_NULL);
         return store.getPorts(deviceId);