Fix use of testharness.js/testharnessreport.js in *.window.js tests

[foolip]

These scripts are already included in the template that turns
*.window.js into *.window.html. Including the twice leads to the error
"Identifier 'MessageQueue' has already been declared" in these tests
when run using wptrunner. MessageQueue is a class declared here:
https://github.com/web-platform-tests/wpt/blob/master/tools/wptrunner/wptrunner/testharnessreport.js

There's also one case of testharness-helpers.js being removed. That file
doesn't exist, and the assert_promise_rejects_with_message helper is
defined by /bluetooth/resources/bluetooth-test.js.

Add timeout=long for tests that took close to 10 seconds run and then
passed. These were flagged as slow tests by the Taskcluster stability
checks.

[foolip]

@WeizhongX FYI this is a case of a problem that only appears with wptrunner, so we haven't noticed this when developing tests in Chromium. Might be an example to add to "bad things that can happen when we don't use the same setup across CIs to run tests."

[domenic]

LGTM, although it might be worth creating a lint rule for this at some point to prevent regressions.

[foolip]

I've filed #36071 for the lint.

[foolip]

So 4 of the tests take close to 10 seconds to run. navigation-helpers.window.html in both Chrome and Firefox, and 3 tests in /permissions-policy/experimental-features/ in just Chrome. I'll add // META: timeout=long to these tests.

[WeizhongX]

@WeizhongX FYI this is a case of a problem that only appears with wptrunner, so we haven't noticed this when developing tests in Chromium. Might be an example to add to "bad things that can happen when we don't use the same setup across CIs to run tests."

Ack!