UWP TextBox will Fill of the Page if they display text with too many combining marks

Describe the bug

When we use the TextBox to display text with too many combining marks that the TextBox will fill with the Page and then it can fix after we focus the TextBox.

Steps to reproduce the bug

Steps to reproduce the behavior:

1. Create a TextBox in xaml
2. Display text with too many combining marks

xaml:

    <Grid>
        <TextBox x:Name="Txt" HorizontalAlignment="Center" VerticalAlignment="Center"></TextBox>
    </Grid>

code:

        public MainPage()
        {
            this.InitializeComponent();

            Txt.Text = new string('\u0483', 550);
        }

Then you can see the Screenshots after you run the application.

Expected behavior

At startup, the TextBox fills the entire page.

Screenshots

Version Info

NuGet package version:

Microsoft.NETCore.UniversalWindowsPlatform 6.1.9

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
October 2018 Update (17763)	Yes
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)
Anniversary Update (14393)

Device form factor	Saw the problem?
Desktop	Yes
Mobile
Xbox
Surface Hub
IoT

Additional context

See https://github.com/dotnet/wpf/issues/244

[chingucoding]

@StephenLPeters Since this is a TextBox internal issue, I think needs to wait until WinUI 3 arrives.

[github-actions[bot]]

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