js: Add _ref property in view,store ref, for combine action in mobx

doric-js/bundle/doric-lib.es5.js

@@ -425,6 +425,7 @@ var View = /** @class */ (function () {
     Object.defineProperty(View.prototype, "ref", {
         set: function (ref) {
             ref.current = this;
+            this._ref = ref;
         },
         enumerable: false,
         configurable: true

doric-js/bundle/doric-lib.js

@@ -345,6 +345,7 @@ class View {
     }
     set ref(ref) {
         ref.current = this;
+        this._ref = ref;
     }
     doAnimation(context, animation) {
         return this.nativeChannel(context, "doAnimation")(animation.toModel()).then((args) => {

doric-js/bundle/doric-vm.js

@@ -1875,6 +1875,7 @@ class View {
     }
     set ref(ref) {
         ref.current = this;
+        this._ref = ref;
     }
     doAnimation(context, animation) {
         return this.nativeChannel(context, "doAnimation")(animation.toModel()).then((args) => {