Update required owned element for role 'combobox' and required context role for role 'option'

[iamrafan]

Considering

• HTML-AAM: select element should map to listbox role regardless of presentation html-aam#46 (comment)
• HTML <select> element can be either combobox or a listbox and can own <option> element with role option

I propose the following changes in ARIA spec

• Add role option as one of the possible "Required owned elements" for combobox
  

• Add role combobox as one of the possible "Required Context roles" for option
  

[mcking65]

As described in w3c/html-aam#46, the plan to resolve is to map html:select@size=1 to a collapsable listbox. I summarized in issue #817 as well.

Allowing option as a child of combobox does not fit the definition of ARIA combobox, which requires a textbox. Doing so would essentially make combobox indistinguishable from listbox. It would also create a scenario where a textbox and an option could be siblings in the same widget, complicating authoring and validation as well as AT support.

I suggest we close this issue as it does not align with the resolution plan we have agreed upon for w3c/html-aam#46.

[jnurthen]

As noted in the previous comment this should be closed