[remoting][FTL] Add telemetry service proto

This CL adds protos to be used by the new remoting-api-based telemetry
service.

Bug: 966993
Change-Id: Ibdc88736340f6176e3695b72a5dab3d6bf35e0e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1629174
Commit-Queue: Yuwei Huang <yuweih@chromium.org>
Reviewed-by: Joe Downing <joedow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663252}
4 files changed