metrics: Convert timestamp and depot_tools_age to integers.
metrics: Convert timestamp and depot_tools_age to integers.

TBR=ajp@chromium.org

Change-Id: I839997c132ad7b9642e795b9562bf4fea18211f4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1585271
Commit-Queue: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>
Reviewed-by: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools