This was the only field not initialized by the constructor, which
looks like an oversight.

Change-Id: If61424d574c663113a4c6d31e94b6ec13b412884
Reviewed-on: https://chromium-review.googlesource.com/257360Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>