Re: [mediacapture-screen-share] Revisit: Let getDisplayMedia() influence the default type choice in the picker (#184)

I believe some good progress was made yesterday at the WebRTC Working Group's September interim meeting. IIUC, the following issues remains:

### 1. Constraints
@youennf voiced a preference to use something other than constraint. @youennf, could you present the alternative you would favor?

### 2. Using "ideal"
Unless we use a mechanism other than constraints, we will only allow `ideal` constraints for displaySurface. Agreed?

### 3. Warning for self-capture
@jan-ivar expressed a strongly held belief that we must specify that the user agent MUST warn the user about self-capture. I am fine with that. Shall we jump on that?

I suggest adding this line to the spec, in a general place, and not specific to display-surface-type-influencing:
```
The user agent MUST strongly warn the user about the dangers of self-capture.
```

### 4. Risky surface types
I agree that the user agent should be allowed to stop the application from influencing the user towards riskier surfaces.
I disagree with the notion that we should draw the line for the user agent.
I propose this formulation:
```
Define as [the user agent's default displaySurface] that surface type which
the user agent presents most prominently when no displaySurface constraint
is specified.

The user agent MUST ignore the displaySurface constraint,
if adhering to this constraint would make the user agent present
as most prominent a surface type which is riskier than its default.
```
With this in place:
1. The text is future-proof for the introduction of future display surface types (think @jan-ivar's `origin-isolated application` for instance).
2. The text works equally well for UAs where the current default is `screen` and for those which have a different default.
3. The text allows `screen` to be meaningfully employed by user agents whose pickers differentiate the current screen from secondary screens. (Modulo difficulties arising from moving browser surfaces between screens - can be addressed in the future.)

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Received on Tuesday, 21 September 2021 16:57:56 UTC