Micro draft of getSupportedTypes()

[yellowdoge]

@foolip can you take a look at the proposed method and let me know what you think, if it's pro forma etc?

Also, can a function be static and return a Promise<> ? :)

Relates to #59.

[foolip]

Static methods can return promises, here are two examples I found by grepping Blink:
https://notifications.spec.whatwg.org/#dom-notification-requestpermission
https://w3c.github.io/webrtc-pc/#sec.cert-mgmt

However, in this case it seems odd that you can synchronously ask if a type is supported, but asking for the supported types is async. What kind of implementation would actually have this restriction? In other words, can't getSupportedTypes also be sync?

[yellowdoge]

getSupportedTypes() might need to check which codecs are/can be e.g. hardware accelerated, whereas isTypeSupported() can answer questions more easily (checking on a list, essentially).

An example: H264 is supported in Chrome/Blink in all cases in Sw and, for certain platforms and hardware configurations, by a encode accelerator. isTypeSupported() knows is supported, whereas getSupportedTypes() might need to dig into lower levels of the implementation for to bump up this format in the list.

[foolip]

It returns a promise, not a sequence directly. Wording more in the style of https://notifications.spec.whatwg.org/#dom-notification-requestpermission would be nice :)

[foolip]

Ah, the order tells you additional information, I didn't read very carefully. It makes sense, concept LGTM.

[foolip]

BTW, do you have someone to more carefully review spec changes, or am I it here?

[yellowdoge]

Too many rebases :)
Will close this PR and open another fresh one.