- Fix Undo/Redo mechanism.
- Finish drawing when the tool is to be chanaged and when the file is to be saved.
- Add ToolBase::OnFinishDraw to virtualize finishing drawing.
- Extend bClearRedo parameter to ImageModel::Undo.
- Add ImageModel::DrawSelectionBackground and ImageModel::DeleteSelection methods.
- Fix some WM_PAINT message handling.
CORE-17969