Fix gn bootstrap

R=dpranke

Change-Id: I469e7e478141e7c389f7a16a5e860122785bab44
Reviewed-on: https://chromium-review.googlesource.com/1072740
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#561663}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 8aca6d50942218ba7887b8b41a44e4f1b7d6f091