Bug 263621 – Log to the console when preventDefault() is called inside a passive event listener

• Status: NEW
• Component: DOM

[Abrar Rahman Protyasha]

The DOM standard makes this recommendation:

```
There are scenarios where invoking preventDefault() has no effect. User agents are encouraged to log the precise cause in a developer console, to aid debugging.
```

We should respect that for the case when preventDefault() is called on an event inside a passive event listener, since that has no effect and might not be what the developer is expecting.

[Radar WebKit Bug Importer]

<rdar://problem/117440707>

[Abrar Rahman Protyasha]

(In reply to Abrar Rahman Protyasha from comment #0)
> The DOM standard makes this recommendation:

Recommendation is here:

https://dom.spec.whatwg.org/#set-the-canceled-flag:~:text=There%20are%20scenarios%20where%20invoking%20preventDefault()%20has%20no%20effect.%20User%20agents%20are%20encouraged%20to%20log%20the%20precise%20cause%20in%20a%20developer%20console%2C%20to%20aid%20debugging.

[Abrar Rahman Protyasha]

This change should also bring us to parity with behavior in Blink/Gecko.

[Abrar Rahman Protyasha]

Pull request: https://github.com/WebKit/WebKit/pull/19514