canInclude(variant, compareCodecs = true) {
    return shaka.media.AdaptationSet
        .areAdaptable(this.root_, variant, compareCodecs);
  }
Check if |variant| can be included with the set. If |canInclude| returns
|false|, calling |add| will result in it being ignored.

@param {shaka.extern.Variant} variant
@param {boolean=} compareCodecs
@return {boolean}