When EditContext.updateSelection is called with offset between a surrogate pair, what should happen?

[masayuki-nakano]

Options:

1. Align to start and/or end of surrogate pair(s)
2. Throw an exception
3. Do nothing

Perhaps, w3c/editing#1 is reasonable. If selectionStart is middle of a surrogate pair, align to start (or end?) of the surrogate pair. If selectionEnd is middle of a surrogate pair, align to end (or start?) of the surrogate pair. (but if the range is collapsed in a surrogate pair, this logic extends the range, perhaps, this would cause unexpected behavior.)

[masayuki-nakano]

And also updateText method shouldn't split surrogate pairs.