GitLab

This CL removes signature and sequence ID from the heartbeat request
since they are no longer required by the server. It also rewrites
HeartbeatSenderTest to mock the HeartbeatClient directly instead of
creating in process channel and mocking the server, so that the tests
can be more deterministic.

Bug: 971363
Change-Id: I3b9be0819172d06da657536c56744532df39a75e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1653602
Commit-Queue: Joe Downing <joedow@chromium.org>
Reviewed-by: Joe Downing <joedow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669093}