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As per issue 78507, we are looking to add support for SQLite databases
to use Write-ahead logging (https://www.sqlite.org/wal.html) mode in
Chromium. WAL mode should give us significant performance gains across
almost all use-cases.

This change is a first step towards achieving this. It adds opt-in
support to enable WAL mode for a database connection and perform a
checkpoint. It also adds a feature flag to enable WAL mode for all
databases by default to investigate its feasibility and impact on
performance.

Bug: 78507
Change-Id: I7fc5edcc39b50d2a13755d587cf342bded1af60a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2095927
Commit-Queue: Shubham Aggarwal <shuagga@microsoft.com>
Reviewed-by: Brandon Maslen <brandm@microsoft.com>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Reviewed-by: Chris Mumford <cmumford@google.com>
Cr-Commit-Position: refs/heads/master@{#780318}