HTML-AAM: determine right mappings for popup ui for input type=color

[jasonkiss]

From @cyns on May 6, 2016 20:20

The color picker dialog that pops up from input type=color is not reliably mapped to accessibility APIs in browsers and does not reliably work with screen readers. We need to determine the right way to map the relationship between the launcher (button or edit) and popup UI, so that screen readers can find it.

Copied from original issue: w3c/aria#363

[jasonkiss]

From @cyns on May 6, 2016 22:7

Here's what we're doing in UIA:
Control Type: Button
Localized Control Type: color picker
ControllerFor: points to the popup
The popup and its children must be present in the UIA tree, and mapped as button, slider, etc. as appropriate for the type of control.

Would it work to do something similar with ControllerFor/ControlledBy in IA2 and ATK?

[jasonkiss]

I've updated the mappings accordingly with fd1e1c2, and added a comment regarding the mapping of associated UI controls when implemented as a color picker. Feel free to reopen if any concerns.