WPF. Bug with ViewPort position in the grid with frozen cell

[EgorDudarev]

Describe the bug
Hi. When grid has frozen rows or frozen columns then after SetColumnsWidth or SetRowsHeight in frozen area other viewports not change StartView property in ViewPort.

Steps to reproduce the behavior:
This behavior can be seen in demo project.

1. Start "WPFDemo.exe"
2. Select cell A9
3. Select menu item Sheet -> Freeze To Cell
4. Increase 6th row height by 2 times
5. See error (8th row displayed twice)

Expected behavior
8th row displayed once

Edition

• WPF

Screenshot

Environment (please complete the following information):

• OS: Windows 10
• Language of OS: any

[jingwood]

Happening in both Windows Form and WPF. Caused by #315