Clipboard API Tests: Move permissions tests to WPT.

[chromium-wpt-export-bot]

Since #20461 and
#5671 were fixed, it now
becomes possible to automate some Web Platform Tests, and have them run
on all browsers automatically.

Clipboard API permission tests were previously outside WPT in order to
automate permissions using PermissionsHelper and detect regressions.

This allows us to share our permissions tests with other browsers
testing using WPT.

Bug: 1076691
Change-Id: I1ff6a8bbdf60b8d77fd8621efce840739fbeec23
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2200278
Auto-Submit: Darwin Huang <[email protected]>
Commit-Queue: Victor Costan <[email protected]>
Reviewed-by: Victor Costan <[email protected]>
Cr-Commit-Position: refs/heads/master@{#769171}

[wpt-pr-bot]

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

[LukeZielinski]

A few of the new tests are flaky on Chrome dev:

Unstable results

Test	Subtest	Results	Messages
/clipboard-apis/permissions/readText-denied.https.html		OK: 9/10, TIMEOUT: 1/10
/clipboard-apis/permissions/readText-denied.https.html	navigator.clipboard.readText() fails when permission denied	PASS: 9/10, TIMEOUT: 1/10	Test timed out
/clipboard-apis/permissions/readText-granted.https.html	navigator.clipboard.readText() succeeds when permission granted	FAIL: 1/10, PASS: 9/10	promise_test: Unhandled rejection with value: object "NotAllowedError: Read permission denied."
/clipboard-apis/permissions/writeText-denied.https.html	navigator.clipboard.writeText() fails when permission denied	FAIL: 1/10, PASS: 9/10	assert_unreached: Should have rejected: undefined Reached unreachable code
/clipboard-apis/permissions/writeText-granted.https.html	navigator.clipboard.writeText() succeeds when permission granted	FAIL: 1/10, PASS: 9/10	promise_test: Unhandled rejection with value: object "NotAllowedError: Write permission denied."

[LukeZielinski]

Files crbug.com/1083268. @Hexcles could you please admin merge?

[dway123]

As per #23332 (comment), this flakiness should now be fixed.