Re: [mediacapture-image] Deny mandatory PTZ contraints in basic getUserMedia contraints (#261)

I also recommend we switching to patching algorithms¹ for greater specificity, since constraints are used in both `getUserMedia` and `applyConstraints`, and the current prose makes it hard to tell where it applies (`getUserMedia` only right?)

As to how to write input validation steps to throw on `exact` ptz constraints, there's precedent in [getDisplayMedia](https://w3c.github.io/mediacapture-screen-share/#dom-mediadevices-getdisplaymedia), so I would look at that:

_"4. For each existing member in constraints whose value, CS, is a dictionary, run the following steps: ... If CS contains a member whose name specifies a constrainable property ..., and whose value in turn is a dictionary containing a member named either min or exact, return a promise rejected with a newly created TypeError."_

We should probably also throw `TypeError`, not `OverconstrainedError`, to be consistent with that precedent.

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<sub>1. I did some algorithm patching a while ago [here](https://w3c.github.io/webrtc-identity/identity.html#creating-an-offer), if you need an example.</sub>

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Received on Thursday, 24 September 2020 18:31:41 UTC