[patch] [ccla] add aria-readonly property to the grid and to cells as appropriate

[Becky Gibson]

Currently waiting for clarification from the ARIA spec on how this should be implemented. Proposal was made that for grid, the default readonly value should be true (rather than false as it is for input fields). Then, readonly=false would be set on editable grid cells rather than having to set readonly=true on non-editable cells.

[Becky Gibson]

May 19 version of the ARIA spec (​http://www.w3.org/WAI/PF/aria/#grid) indicates that the default for grid is readonly=false, the grid IS editable, and the readonly value of the grid is propagated to the contained gridcells.

If the DataGrid? contains editable cells, there is no need to set the aria-readonly property on the grid since readonly=false is the default. Each non-editable cell must be marked with aria-readonly=true. The editable cells do NOT need to have an aria-readonly property added since they inherit from the grid.

If the grid does NOT contain any editable cells, set aria-readonly=true on the grid. Each individual cell will inherit this value and thus does not need the readonly property set.

Since the DataGrid? does not currently support editing column headers, those cells get aria-readonly=true, irregardless of the readonly setting of the grid.

[Becky Gibson]

contains console statements that will be removed before commit

[Becky Gibson]

(In [18456]) Fixes #9176 Add ARIA readonly property on the grid and cells as appriopriate see ticket for implementation details. Fixes 9428 remove id on grid view pages as the ids were not used and duplicated when there were multiple views. !strict