If a user selected the text "foo" and typed "bar", upon pressing undo,
the text would change to "b". This is incorrect and does not match the
functionality of QLineEdit or the default behaviours of Windows/OSX/Ubuntu.
This was fixed by a change made to always merge two sequential inserts
if they are not part of the same block. Previously the selection delete
and the "b" were part of one edit block and "ar" was part of another.
With this change, the selection delete and "bar" are part of the same
edit block.
Unit test changes are part of a separate review (Part #1) since they
required changes in qtdeclarative.
[ChangeLog][QtGui][Important Behavior Changes] Fixed QTextEdit to match
undo functionality of QLineEdit to group two sequential inserts into one
undo action.
Task-number: QTBUG-38825
Change-Id: I76bf30e331e3526277c3e0ade58cf95b611fc117
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>