Need to add properties Client-Id and Channel to GoogleMapsDirections Element

[Mat Gutschow]

See thread #313 for more...

The client-id property isn't exposed on the google-map-directions element, but it is exposed on the google-map element:

<dom-module id="google-map-directions">
  <style>
    :host {
      display: none;
    }
  </style>
  <template>
    <google-maps-api
      api-key="[[apiKey]]"
      language="[[language]]"
      on-api-load="_mapApiLoaded"></google-maps-api>
  </template>
</dom-module>

Which results in this error, because I don't have an api-key, only client-id:

However, if I add the client-id property on the google-map-directions element and pass it to the google-maps-api element it will work as expected and no errors occur.