These classes do a few things:
1. They implement and abstract common text operations, for example:
(a) comparing two markers to know which one precedes the other.
(b) text retrieval for ranges
(c) geometric bounds for ranges
(d) etc.
2. They can be converted to and from AXTextMarker(Range)s. Since the AXTextMarker
should not contain a raw pointer since there is a potential for use-after-free,
we need to lookup the referenced accessible in its document to know that it still exists.
Note: mozTextAccessible got pushed to another unified source file, so we need to
declare some stuff for it. Ideally we would be detecting these kinds of things sooner.
Differential Revision: https://phabricator.services.mozilla.com/D81760
Eitan Isaacson