func NewServerStatsHandler() *ServerStatsHandler {
	return &ServerStatsHandler{}
}
NewServerStatsHandler returns a StatsHandler that can be passed to
grpc.NewServer using grpc.StatsHandler to enable trace context propagation
and automatic span creation for incoming gRPC requests.
package grpctrace
import (
	"strings"
	"go.opencensus.io/trace"
	"go.opencensus.io/trace/propagation"
	"golang.org/x/net/context"
	"google.golang.org/grpc"
	"google.golang.org/grpc/metadata"
	"google.golang.org/grpc/stats"
)
type ClientStatsHandler struct{}
var _ stats.Handler = &ClientStatsHandler{}
func NewClientStatsHandler() *ClientStatsHandler {
	return &ClientStatsHandler{}
}
type ServerStatsHandler struct{}