static filterByRestrictions(manifest, restrictions, maxHwResolution) {
    manifest.variants = manifest.variants.filter((variant) => {
      return shaka.util.StreamUtils.meetsRestrictions(
          variant, restrictions, maxHwResolution);
    });
  }
Filter the variants in |manifest| to only include the variants that meet
the given restrictions.

@param {!shaka.extern.Manifest} manifest
@param {shaka.extern.Restrictions} restrictions
@param {shaka.extern.Resolution} maxHwResolution