Turns out this is required in the situation where the document occupy less space than the visible document rect.
In this case, inserting new lines will not resize the text view, since it has been artificially enlarged to fit the visible document rect, therefore the gutter view will not update properly when inserting new lines.
I think there is a better solution than have the text view refresh the gutter, reverting is just meant as a quick fix.
This reverts commit 4e2ae3c508.
6c6ba400ff