remove unused / redundant mixin observers (#3831)

Author: ngokevin

src/core/a-entity.js

@@ -111,19 +111,6 @@ var proto = Object.create(ANode.prototype, {
     }
   },
 
-  /**
-   * Apply mixin to component.
-   */
-  handleMixinUpdate: {
-    value: function (attrName) {
-      if (!attrName) {
-        this.updateComponents();
-        return;
-      }
-      this.updateComponent(attrName, this.getDOMAttribute(attrName));
-    }
-  },
-
   getObject3D: {
     value: function (type) {
       return this.object3DMap[type];

src/core/a-mixin.js

@@ -22,6 +22,7 @@ module.exports = registerElement('a-mixin', {
     attributeChangedCallback: {
       value: function (attr, oldVal, newVal) {
         this.cacheAttribute(attr, newVal);
+        this.updateEntities();
       }
     },
 

src/core/a-node.js

@@ -1,13 +1,11 @@
-/* global CustomEvent, MutationObserver */
+/* global CustomEvent */
 var registerElement = require('./a-register-element').registerElement;
 var isNode = require('./a-register-element').isNode;
 var utils = require('../utils/');
 
 var warn = utils.debug('core:a-node:warn');
 var error = utils.debug('core:a-node:error');
 
-var MIXIN_OBSERVER_CONFIG = {attributes: true};
-
 /**
  * Base class for A-Frame that manages loading of objects.
  *
@@ -22,7 +20,6 @@ module.exports = registerElement('a-node', {
         this.hasLoaded = false;
         this.isNode = true;
         this.mixinEls = [];
-        this.mixinObservers = {};
       },
       writable: window.debug
     },
@@ -212,7 +209,6 @@ module.exports = registerElement('a-node', {
         // Register mixin.
         this.computedMixinStr = this.computedMixinStr + ' ' + mixinEl.id;
         this.mixinEls.push(mixinEl);
-        this.attachMixinListener(mixinEl);
       }
     },
 
@@ -235,48 +231,9 @@ module.exports = registerElement('a-node', {
             break;
           }
         }
-        this.removeMixinListener(mixinId);
-      }
-    },
-
-    removeMixinListener: {
-      value: function (mixinId) {
-        var observer = this.mixinObservers[mixinId];
-        if (!observer) { return; }
-        observer.disconnect();
-        this.mixinObservers[mixinId] = null;
       }
     },
 
-    /**
-     * Add mutation observer from entity to mixin.
-     */
-    attachMixinListener: {
-      value: function (mixinEl) {
-        var currentObserver;
-        var mixinId;
-        var observer;
-        var self = this;
-
-        if (!mixinEl) { return; }
-
-        mixinId = mixinEl.id;
-        currentObserver = this.mixinObservers[mixinId];
-        if (currentObserver) { return; }
-
-        // Add observer.
-        observer = new MutationObserver(function (mutations) {
-          self.handleMixinUpdate(mutations[0].attributeName);
-        });
-        observer.observe(mixinEl, MIXIN_OBSERVER_CONFIG);
-        this.mixinObservers[mixinId] = observer;
-      }
-    },
-
-    handleMixinUpdate: {
-      value: function () { /* no-op */ }
-    },
-
     /**
      * Emit a DOM event.
      *