Fix gn bootstrap

BUG=837312
R=dpranke

Change-Id: Ia5c57f596388a4ba325208c638fac558984202f0
Reviewed-on: https://chromium-review.googlesource.com/1030895
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#554419}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 0d3bbfb6b8ba05af199b49f5dd71d842f6acffda