Sync with mattermost 3.5.0

vendor/github.com/mattermost/platform/model/webrtc.go

@@ -0,0 +1,21 @@
+package model
+
+import (
+	"encoding/json"
+	"io"
+)
+
+type GatewayResponse struct {
+	Status string `json:"janus"`
+}
+
+func GatewayResponseFromJson(data io.Reader) *GatewayResponse {
+	decoder := json.NewDecoder(data)
+	var o GatewayResponse
+	err := decoder.Decode(&o)
+	if err == nil {
+		return &o
+	} else {
+		return nil
+	}
+}