The text attribute code we use right now lives in BrowserAccessibilityComWin::ComputeTextAttributes(), and should be moved somewhere that the ATK code can benefit, as the text attributes in ATK/IA2 are the same.

Here's info for ATK/IA2 standard names for text attributes, including how their values are formatted, and default values. The value is not exposed when it matches the default value, which greatly decreases the number of attributes exposed and makes things easier to debug as one will generally only see text attributes when something is different from the norm.

https://wiki.linuxfoundation.org/accessibility/iaccessible2/textattributes