fix: call setIsTrusted for generated events (MessageEvent)

[corrideat]

This addresses issue #19918.

Issue description

Event messages have the wrong isTrusted value when they are not triggered by user interaction, which differs from the browser. In particular, all MessageEvents created by Deno have isTrusted set to false, even though it should be true.

This is my first ever contribution to Deno, so I might be missing something.

[CLAassistant]

All committers have signed the CLA.

[corrideat]

The automated tests fail here:

expected test failures that passed:

        "/webmessaging/MessageEvent-trusted.any.html - With a MessageChannel and its MessagePorts"
        "/webmessaging/MessageEvent-trusted.any.html - With a BroadcastChannel"
        "/webmessaging/MessageEvent-trusted.any.worker.html - With a MessageChannel and its MessagePorts"
        "/webmessaging/MessageEvent-trusted.any.worker.html - With a BroadcastChannel"

I believe that those tests are supposed to pass with this change. The corresponding lines in tools/wpt/expectation.json are:

    "MessageEvent-trusted.any.html": false,
    "MessageEvent-trusted.any.worker.html": false,

Should I update these as well in the PR, or is there a reason for them to be supposed to fail?

[bartlomieju]

No other reason besides it wasn't implemented :) you should update these entries to true to make WPT test suite happy.

[crowlKats]

LGTM, thanks