[cssom-view] Return real values for colorDepth and pixelDepth (closes #993)

[mounirlamouri]

Fixes #993

[mounirlamouri]

@zcorpan PTAL

[mounirlamouri]

Thank you for the comments @dbaron. I have applied them apart from the example one: do you have recommendations for a better, less misleading, example? In practices, I would be surprised if the non-comforming implementations also implement the css color gamut which hopefully makes the example not insane in practice but I would be happy to put something else in the spec :)

[dbaron]

While that example itself is fine because such implementations wouldn't match the p3 media query, people might start from that code and modify it to do other things.

Would the high-gamut devices report 48? If so, maybe it's better to test >= 48?

[mounirlamouri]

I've updated the example to use >= 48. It actually makes a lot of sense :)

I've also removed the 24 clamping following discussion with @dbaron and @zcorpan on IRC.

[zcorpan]

Same value seems wrong. The color media query is per component, whereas here is all components together. There's also this complication:

If different color components are represented by different number of bits, the smallest number is used.

I suppose an integer-divide by 3 should give the same value as the color media query?

[mounirlamouri]

@zcorpan, I've rephrased. WDYT?

[zcorpan]

Looks good to me.

[mounirlamouri]

@zcorpan I assume we need @dbaron's lgtm now? :) Is there someone else who should have a look?

[zcorpan]

Final review from @dbaron would be nice.