Fixed GUI pulsing due to PORT_STATS_UPDATE event.

Change-Id: I18b7e8b300f0af6f6cbf453f346808bb1c6d0d3c

@@ -74,7 +74,7 @@ public class DeviceEvent extends AbstractEvent<DeviceEvent.Type, Device> {
          */
         PORT_REMOVED,
 
-        /*
+        /**
          * Signifies that port statistics has been updated.
          */
         PORT_STATS_UPDATED

@@ -72,8 +72,7 @@ import static com.google.common.base.Strings.isNullOrEmpty;
 import static org.onosproject.cluster.ClusterEvent.Type.INSTANCE_ADDED;
 import static org.onosproject.net.DeviceId.deviceId;
 import static org.onosproject.net.HostId.hostId;
-import static org.onosproject.net.device.DeviceEvent.Type.DEVICE_ADDED;
-import static org.onosproject.net.device.DeviceEvent.Type.DEVICE_UPDATED;
+import static org.onosproject.net.device.DeviceEvent.Type.*;
 import static org.onosproject.net.host.HostEvent.Type.HOST_ADDED;
 import static org.onosproject.net.link.LinkEvent.Type.LINK_ADDED;
 
@@ -774,10 +773,12 @@ public class TopologyViewMessageHandler extends TopologyViewMessageHandlerBase {
     private class InternalDeviceListener implements DeviceListener {
         @Override
         public void event(DeviceEvent event) {
+            if (event.type() != PORT_STATS_UPDATED) {
                 sendMessage(deviceMessage(event));
                 eventAccummulator.add(event);
             }
         }
+    }
 
     // Link event listener.
     private class InternalLinkListener implements LinkListener {

@@ -263,7 +263,8 @@
             online = ldata.online(),
             delay = immediate ? 0 : 1000;
 
-        // TODO: understand why el is sometimes undefined on addLink events...
+        // FIXME: understand why el is sometimes undefined on addLink events...
+        if (el) {
             el.classed('link', true);
             el.classed('inactive', !online);
             el.classed(allLinkTypes, false);
@@ -275,6 +276,7 @@
                 .attr('stroke-width', linkScale(lw))
                 .attr('stroke', linkConfig[th].baseColor);
         }
+    }
 
     function removeLinkElement(d) {
         var idx = fs.find(d.key, network.links, 'key'),