ref: Implement the javascript server side of vtrace.

After this CL servers can return new traces and annotations.
I still need to address security.

MultiPart: 1/2

Change-Id: I6232c76e627d417435846a15dd1ac6492d8da4f8
diff --git a/services/wsprd/ipc/server/invoker.go b/services/wsprd/ipc/server/invoker.go
index 196ff2a..2f69c03 100644
--- a/services/wsprd/ipc/server/invoker.go
+++ b/services/wsprd/ipc/server/invoker.go
@@ -7,6 +7,7 @@
 	"v.io/v23/vdl"
 	"v.io/v23/vdlroot/signature"
 	"v.io/v23/verror"
+	"v.io/v23/vtrace"
 )
 
 var typedNil []int
@@ -65,6 +66,8 @@
 		return nil, reply.Err
 	}
 
+	vtrace.GetStore(call.Context()).Merge(reply.TraceResponse)
+
 	// Convert the reply.Results from []*vdl.Value to []interface{}
 	results := make([]interface{}, len(reply.Results))
 	for i, r := range reply.Results {