A11y_.NETCore3.0(WPF)_WPF ControlsAndLayout_Layout Dock panel_ScreenReader: Screen reader focus is not moving in proper logical order.

Copied from VSO [956760](https://devdiv.visualstudio.com/DevDiv/_queries/edit/956760/)

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Environment Details:

Application Name: .NET Core 3.0 (WPF)

.NET Core SDK version: 3.0.100-preview8-013442
Windows Version: Windows10

ScreenReader Version: Narrator, NVDA 2019.1.1

Pre-requisite:

1) Download the latest .NET Core 3 daily build by going to this link.
2) Install Windows (x86 or x64) versions of sdk listed under Master (3.0.x Runtime) by clicking "Installer" link.

Repro Steps:

1) Download the latest .NET Core 3 daily build given on .NET Core daily builds page.
2) Install Windows (x86 or x64) versions of sdk listed under Master (3.0.x Runtime) by clicking "Installer" link.
3) Run exe file for "ControlsAndLayout" from the build app folder provided.
4) Main Window for "ControlsAndLayout" solution will appear.
5) From the Sample Library pane under Layout, select "DockPanel".
6) Turn on screen reader
7) Navigate to main content.

Actual:

Screen reader focus is not moving in proper logical order. i.e. from left to right and then Top to bottom.

Expected:

Screen reader focus should move in proper logical order/

User Impact:

The screen reader user will get confused for content ordering.

Recommendations:

Please refer to below URL which is repository for accessibility bug fixes.

https://microsoft.sharepoint.com/teams/msenable/Pages/Home.aspx

MAS Reference:

MAS 1.3.2:

https://microsoft.sharepoint.com/:w:/r/teams/msenable/_layouts/15/WopiFrame.aspx?sourcedoc={1ee227a7-e3c5-47b8-ab18-48ca8595077b}