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

In the [intro](https://github.com/w3c/mediacapture-image/pull/261#issue-488934739), I stated that some details related to the resolution are not entirely clear to me and that this PR ensures that PTZ constraint cannot cause `getUserMedia()` to fail conditionally. In https://github.com/w3c/mediacapture-image/pull/261#discussion_r493634893 @guidou noted that that is not enough to prevent fingerprinting.

So I have more questions:

- What should `getUserMedia({video: {advanced: [{pan: {exact: 1234}, width: 10}]}` or  `getUserMedia({video: {advanced: [{pan: 1234, width: 10}]}` do? Should the advanced constraint set be ignored? Note that @youennf's PR https://github.com/w3c/mediacapture-main/pull/707 does not do that. If the advanced constraint set is ignored, should it be ignored silently, should it produce a console warning or equivalent or should it throw an `OverconstrainedError` (which advanced constraints do not normally throw)?
- What should `getUserMedia({video: {advanced: [{pan: {ideal: 1234}, width: 10}]}` do? Is that ideal request for pan capability and for the pan setting of 1234?
- What should `getUserMedia({video: {advanced: [{pan: true, width: 10}]}` or  `getUserMedia({video: {advanced: [{pan: {}, width: 10}]}` do? Is that ideal request for pan capability (like `getUserMedia({video: {pan: true}})`)? Makes kind of sense. Or is that no constraint and no capability request? That would be easy but in that case is  `getUserMedia({video: {advanced: [{pan: {ideal: 1234}, width: 10}]}` an ideal request for the pan setting of 1234 but not an ideal request for pan capability which does not make much sense.
- Or should PTZ constraints in the advanced constraint sets be ignored or forbidden in `getUserMedia()` altogether? That might actually make most sense as advanced PTZ constraints in `getUserMedia()` do not really have much value. If that route is selected, should PTZ constraints in the advanced constraint sets be silently ignore, or should they produce a console warning or equivalent or should they throw an `OverconstrainedError`?

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Received on Wednesday, 23 September 2020 15:58:19 UTC