[CORD-2903] Improve SR/Multicast APIs

Change-Id: Id44af87569e0a83129c96504b21c69e1d455f785
(cherry picked from commit a2858a34a26e02e9d2dd66dc562d0f6fb2c4bdd1)
diff --git a/apps/segmentrouting/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java b/apps/segmentrouting/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
index eff78e5..c200d74 100644
--- a/apps/segmentrouting/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
+++ b/apps/segmentrouting/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
@@ -675,6 +675,12 @@
     }
 
     @Override
+    public Multimap<ConnectPoint, List<ConnectPoint>> getMcastTrees(IpAddress mcastIp,
+                                                                    ConnectPoint sourcecp) {
+        return mcastHandler.getMcastTrees(mcastIp, sourcecp);
+    }
+
+    @Override
     public Map<IpAddress, NodeId> getMcastLeaders(IpAddress mcastIp) {
         return mcastHandler.getMcastLeaders(mcastIp);
     }