Re: [mediacapture-fromelement] define behaviors of the common ConstrainablePattern Interfaces

To bring the Constrainable Pattern to the 
`CanvasCaptureMediaStreamTrack` and drawing from my experience with 
ImageCapture https://github.com/w3c/mediacapture-image/pull/146, I 
think roughly here we'd need to define a supported constraints 
dictionary as sth like:

```
partial dictionary MediaTrackSupportedConstraints {
 boolean width = false;
 boolean height = false;
 boolean aspectRatio = false;
 boolean frameRate = true;
 boolean facingMode = false;
 boolean volume = false;
 boolean sampleRate = false;
 boolean sampleSize = false;
 boolean echoCancellation = false;
 boolean latency = false;
 boolean channelCount = false;
 boolean deviceId = false;
 boolean groupId = false;
};
```

and also the behaviour of the rest of the Constrainable Pattern 
methods that are needed as well, i.e. these guys:

```
MediaTrackCapabilities getCapabilities ();
MediaTrackConstraints getConstraints ();
MediaTrackSettings getSettings ();
Promise<void> applyConstraints (optional MediaTrackConstraints 
constraints);
```

And to round the change, `captureStream()` should accept a 
[`MediaTrackConstraintSet`](https://www.w3.org/TR/mediacapture-streams/#dictionary-mediatrackconstraints-members)
 a la `getUserMedia()`.

We should also have a similar analysis for the "standard" 
MediaStreamTrack produced by `captureStream()` on an HTMLMediaElement.

ImageCapture has a rendering of my proposed PR in 
https://rawgit.com/Miguelao/mediacapture-image/pr001_constrainable_pattern/index.html


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Received on Friday, 10 February 2017 19:34:38 UTC