Add event handler attributes (e.g. onkeystatuseschange on MediaKeySession)

[foolip]

Justification is the same as in w3c/media-source#66 and this issue should probably block on the resolution of that.

[ddorwin]

Based on w3ctag/design-principles#29 (comment), we should have event handler attributes for all of our events.

We need to add attributes for both MediaKeySession events:

• onkeystatuseschange
• onmessage

Of the HTMLMediaElement events:

• We already have onencrypted.
• We need to add onwaitingforkey.

[jdsmith3000]

This is a clearly defined change that is ready for implementation.

[foolip]

See w3c/html#335 (comment) for a detail you'll need to decide on.

[ddorwin]

@foolip, does this only apply to the two HTMLMediaElement event handlers?

@domenic said, "So I guess if it bubbles it belongs there." Related to bubbling, the spec text currently says:

• "Queue a task to create an event named encrypted that does not bubble* and is not cancellable..."
• "Queue a task to fire a simple event named waitingforkey at the media element."
  • Per HTML5, "Firing a simple event named e means that a trusted event with the name e, which does not bubble (except where otherwise stated) and is not cancelable (except where otherwise stated)..."

Thus, it would seem there is no bubbling and thus no need to put these on the GlobalEventHandlers. However, HTML5 also uses the "fire a simple event" language for play, playing, and likely others, which seems inconsistent with @domenic's guidance.

[foolip]

Yeah, all events in HTML are on GlobalEventHandlers even if they don't bubble, for simplicity I suppose.

I would go with extending HTMLMediaElement only, since it's easier to move in the direction of GlobalEventHandlers than moving away from it.

[ddorwin]

@jdsmith3000, this is ready for implementation per the original plan.

[jdsmith3000]

The original plan included adding attributes for MediaKeySession events:

• onkeystatuseschange
• onmessage

And HTMLMediaElement events:

• Done already: onencrypted
• Need: onwaitingforkey

Please confirm that we now only need to add an attribute for onwaitingforkey to the HTMLMediaElement extensions.

I'm preparing this change now.

[ddorwin]

I don't believe anything has changed with respect to MediaKeySession and we should add those two event handler attributes as well. Yes, the only change to HTMLMediaElement is to add onwaitingforkey.

[ddorwin]

Fixed by 3d4a9ce.