text: /*
   * Copyright 2016 Google Inc. All rights reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  'use strict';
  
  var StaticAsset = require('./Static');
  var inherits = require('../util/inherits');
  var eventEmitter = require('minimal-event-emitter');
  var clearOwnProperties = require('../util/clearOwnProperties');
  
  /**
   * @class DynamicAsset
   * @implements Asset
   * @extends StaticAsset
   * @classdesc
   *
   * An {@link Asset} whose pixel contents may change.
   *
   * @param {HTMLImageElement|HTMLCanvasElement|ImageBitmap} element The
   *     underlying pixel source.
   * @throws If the pixel source is unsupported.
   */
  function DynamicAsset(element) {
    this.constructor.super_.call(this, element);
    this._timestamp = 0;
  }
  
  inherits(DynamicAsset, StaticAsset);
  eventEmitter(DynamicAsset);
  
  /**
   * Destructor.
   */
  DynamicAsset.prototype.destroy = function() {
    clearOwnProperties(this);
  };
  
  DynamicAsset.prototype.timestamp = function() {
    return this._timestamp;
  };
  
  DynamicAsset.prototype.isDynamic = function() {
    return true;
  };
  
  /**
   * Marks the asset dirty, signaling that the contents of the underlying pixel
   * source have changed.
   *
   * @throws If the asset is not dynamic.
   */
  DynamicAsset.prototype.markDirty = function() {
    this._timestamp++;
    this.emit('change');
  };
  
  module.exports = DynamicAsset;
  