Quota: Remove unreported member from QuotaTemporaryStorageEvictor::Statistics.

The `num_errors_on_evicting_origin` member used to be reported to UMA
but has since expired and been removed. This change cleans it out as
it's no longer being used outside of chrome://quota-internals.

The `num_errors_on_getting_usage_and_quota` member was another stat
that was used to report on an expired UMA histogram. However, this
change does not clean out that member because it is still used in
setting a cap on the number of retries after unsuccessful attempts to
get usage and quota info.

Bug: 939513
Change-Id: I9da6e44dfdc2e4e4b93c9cea04eb923501c81557
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1515652
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639592}
3 files changed