The total line count needs to be updated when geometry,
document size or wrapping mode changes.

Task-number: QTBUG-37263
Change-Id: If58a2f77022475e8bcb7cca0f2a091ee837b39a5
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>
Reviewed-by: Caroline Chao <caroline.chao@digia.com>