SizeDefinition property of RibbonControls in RibbonToolBar is not reflected in layout

[nishy2000]

SizeDefinition property of RibbonControls in RibbonToolBar is not reflected in layout

How to reporoduce:

1. Add the following code as new RibbonTabItem in TestContent.xaml.

<Fluent:RibbonTabItem Header="Ribbon controls in panel"
                                  ReduceOrder="PanelGroup11,PanelGroup11,PanelGroup11,PanelGroup11"
                                  KeyTip="P">
    <Fluent:RibbonGroupBox x:Name="PanelGroup11"
                       Header="In RibbonToolBar"
                       LauncherText="launcher"
                       Icon="pack://application:,,,/Fluent.Ribbon.Showcase;component/Images/Green.png"
                       IsSeparatorVisible="True"
                       IsLauncherVisible="True">

    <Fluent:RibbonToolBar>
        <Fluent:Button Header="Full(L/L/S) button"
                       Icon="pack://application:,,,/Fluent.Ribbon.Showcase;component/Images/Gray.png"
                       LargeIcon="pack://application:,,,/Fluent.Ribbon.Showcase;component/Images/GrayLarge.png"
                       SizeDefinition="Large,Large,Small"/>
        <Fluent:Button Header="Full(M/M/S) button"
                       Icon="pack://application:,,,/Fluent.Ribbon.Showcase;component/Images/Yellow.png"
                       LargeIcon="pack://application:,,,/Fluent.Ribbon.Showcase;component/Images/YellowLarge.png"
                       SizeDefinition="Middle,Middle,Small"/>
        <Fluent:Button Header="Full(L/L/L) button"
                       Icon="pack://application:,,,/Fluent.Ribbon.Showcase;component/Images/Orange.png"
                       LargeIcon="pack://application:,,,/Fluent.Ribbon.Showcase;component/Images/OrangeLarge.png"
                       SizeDefinition="Large"/>
        <Fluent:Button Header="Full(default) button"
                       Icon="pack://application:,,,/Fluent.Ribbon.Showcase;component/Images/Brown.png"
                       LargeIcon="pack://application:,,,/Fluent.Ribbon.Showcase;component/Images/BrownLarge.png" />
        </Fluent:RibbonToolBar>
    </Fluent:RibbonGroupBox>
</Fluent:RibbonTabItem>

2. Start Fulent.Ribbon.Showcase
3. Show a added new ribbon tab item
4. SizeDefinition property of RibbonControls in RibbonToolBar is not reflected in layout when showing at first and when changing State property of RibbonGroupBox

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Environment

• Fluent.Ribbon 9.0.0 preview (latest develop branch [69f4464])
• Windows 10 Pro 20H2
• .NET Framework 4.6.2 / net5.0-windows