We have some unexpected/unexplained Telemetry session data resets (at least for the profileSubsessionCounter). We need to track the save & load failures for the session data file to investigate.

Comment on attachment 8642375 [details] [diff] [review] Add probes for Telemetry session data load & save failures Approval Request Comment [Feature/regressing bug #]: Telemetry Unification [User impact if declined]: This adds diagnostics for when we fail to load or save persisted session data - we need this for validating the incoming data and detecting issues. It is part of a mostly fixup & diagnostic uplift batch for 41: http://bit.ly/1LYhA16 [Describe test coverage new/current, TreeHerder]: We have automated test-coverage, it baked on Nightly, we are monitoring it. [Risks and why]: Low-risk, we haven't seen anything crop up on Nightly here. [String/UUID change made/needed]: None.

Comment on attachment 8642375 [details] [diff] [review] Add probes for Telemetry session data load & save failures [Triage Comment] Fix has automated tests, and code has been in Nightly for a week so should be safe to uplift to Beta.