check and consume user activation

[marcoscaceres]

Closes #346

The following tasks have been completed:

• Modified Web platform tests

Implementation commitment:

• Chromium (https://bugs.chromium.org/p/chromium/issues/detail?id=)
• Gecko (https://bugzilla.mozilla.org/show_bug.cgi?id=1772051)
• WebKit - https://bugs.webkit.org/attachment.cgi?id=455337&action=review

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Preview | Diff

[marcoscaceres]

Preparing a WPTest...

[beverloo]

I'm not sure this is Web compatible -

1. subscribe() can be called from within a service worker, where there are no local activations that can be consumed -- particularly the consume user activation steps assume that there's a window.
2. Looking at our metrics, only about a fourth of permission requests happen with a gesture. We mitigate against this by displaying a different user interface (if any at all) in those cases. In my reading it would be valid for an implementation not to show any prompt at all.

[saschanaz]

Note that Gecko opted to require user activation only if the permission is not granted, and just proceeds without activation if it's granted, which I think is the best way as reportedly some websites repeatedly calls pushManager.subscribe() every time: https://bugzilla.mozilla.org/show_bug.cgi?id=1486010#c5

Instead, the page calls pushManager.subscribe every time you visit it

[marcoscaceres]

I'll take a closer look at what WebKit does... we might be doing something similar @saschanaz.

[saschanaz]

I'm fine with this.

[saschanaz]

The Gecko implementation is more like saving the transient activation state and use that info later in async, but maybe that's a bit unusual to specify?

[annevk]

What happens if someone else consumes it meanwhile?

[saschanaz]

Ah yes, we only check the activation but doesn't really consume it, that's why we can do that. Certainly things would change when we consume it.

[annevk]

I should queue a task here and not just return a fresh promise. I do think we want to consume immediately and not from a task. Otherwise it's not very predictable for web developers.