WPT: Upstream and add some transaction scheduling tests

[chromium-wpt-export-bot]

In service of w3c/IndexedDB#253 move some
transaction scheduling tests from Blink to WPT.

This involved converting them from js-test.js to testharness.js, but
the overall logic of each test was retained.

This also adds one new test which verifies the change described
in w3c/IndexedDB#319 - all browsers implicitly
block R-O transactions behind overlapping R/W transactions.

Change-Id: I596aaa75b79bf3bf3e17a2553abb4e11329d59ab
Bug: 921193
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2081237
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Joshua Bell <jsbell@chromium.org>
Auto-Submit: Joshua Bell <jsbell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#746553}

[wpt-pr-bot]

The review process for this patch is being conducted in the Chromium project.

[inexorabletash]

wpt-firefox-nightly-stability

/IndexedDB/transaction-lifetime-blocked.htm
Blocked event | FAIL: 4/10, PASS: 6/10 | assert_unreached: open.error (VersionError) Reached unreachable code

/IndexedDB/transaction-lifetime.htm
Test events opening a second database when one connection is open already | FAIL: 5/10, PASS: 5/10 | assert_unreached: open.error (VersionError) Reached unreachable code

Pre-existing?

[inexorabletash]

I can repro the failures of those tests in FF locally by reloading the files a few times.

[inexorabletash]

FWIW, both of those tests will fail if another test leaves a database named 'db' with a version higher than 3; it doesn't proactively delete the database before trying to use it.

Tests that use 'db' as a name look like they all have add_completion_callback() handlers which attempt to delete the database. Maybe if FF doesn't let that run and/or aborts the delete if the page unloads it would be left behind.

A good fix would be to use a unique database name per test, as is done in most places.

[inexorabletash]

Putting up a Chrome CL to address that flakiness. https://chromium-review.googlesource.com/c/chromium/src/+/2086452/

[stephenmcgruer]

Thanks for proactively looking at this! Since there's a fix in flight, I'm going to admin-merge this.