websql: Use a dedicated SQLite VFS.

This is the first step in removing our SQLite VFS patches that support
WebSQL. After this CL proves stable, a follow-up will remove the SQLite
patches.

Bug: 925739
Change-Id: I9c709242f815ffa4e97787c37cea247a222c9990
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1438818
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Chris Mumford <cmumford@google.com>
Reviewed-by: Joshua Bell <jsbell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641417}
14 files changed