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This CL revises adds metrics for stability instrumentation
collection on crash. The metrics can be used to estimate unclean
shutdown coverage in combination with postmortem collection (see
https://crrev.com/2883103002).

Additionally addresses a todo: sets the persitent allocator state to
deleted on crash.

BUG=620813

Review-Url: https://codereview.chromium.org/2910003002
Cr-Commit-Position: refs/heads/master@{#476319}