function defineProperties(obj, props) {
  const keys = Object.keys(props)
  for (let i = 0; i < keys.length; ++i) {
    const key = keys[i]
    defineProperty(obj, key, props[key])
  }
}
Adds several properties to the given object.

@memberof Shim.prototype
@param {object} obj    - The object to add the properties to.
@param {object} props  - A mapping of properties to values to add.
@see Shim#defineProperty