Previously this API didn't work unless some other API
had first been called to load the data.

Change-Id: Iff9b36c48b45b64dc2f9b95230955858501903dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2528111Reviewed-by: Dirk Pranke <dpranke@google.com>
Commit-Queue: Adrian Taylor <adetaylor@chromium.org>