[CRD iOS] Report session entry point in telemetry

This CL adds the session entry point info to the telemetry reported by
the iOS client. This allows us to compare metrics on initial vs reconnect
attempt, and reuse error breakdown dashboard without unchecking the
SessionEntryPoint filter.

Bug: 840556
Change-Id: I27b5fd644f024b10953b5bbf919047d8f370b753
Reviewed-on: https://chromium-review.googlesource.com/1141147
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Commit-Queue: Yuwei Huang <yuweih@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576952}
10 files changed