To avoid being able to introduce dependencies between tests this commit
makes sure that we close the document between tests so that we can't
accidentally rely on state set by a previous test.
Debugging #17931 uncovered a race condition in the way we use the
`waitForEvent` function. Currently the following happens:
1. We call `waitForEvent`, which starts execution of the function body
and immediately returns a promise.
2. We do the action that triggers the event.
3. We await the promise, which resolves if the event is triggered or
the timeout is reached.
The problem is in step 1: function body execution has started, but not
necessarily completed. Given that we don't await the promise, we
immediately trigger step 2 and it's not unlikely that the event we
trigger arrives before the event listener is actually registered in the
function body of `waitForEvent` (which is slower because it needs to be
evaluated in the page context and there is some other logic before the
actual `addEventListener` call).
This commit fixes the issue by passing the action to `waitForEvent` as
a callback so `waitForEvent` itself can call it once it's safe to do so.
This should make sure that we always register the event listener before
triggering the event, and because we shouldn't miss events anymore we
can also remove the retry logic for pasting.
The integration tests are currently not consistent in how they do
copy/pasting: some tests use the `kbCopy`/`kbPaste` functions with
waiting for the event inline, some have their own helper function to
combine those actions and some even call `kbCopy`/`kbPaste` without
waiting for the event at all (which can cause intermittent failures).
This commit fixes the issues by providing a set of four helper functions
that all tests use and that abstract e.g. waiting for the event away
from the caller. This makes the invididual tests simpler and consistent,
reduces code duplication and fixes possible intermittent failures
due to not waiting for events to trigger.
