[iOS][NavigationBar] Complex Content is not measured properly upon device rotation

[kazo0]

When setting the Content property of the NavigationBar to a complex UI element, like:

<utu:NavigationBar.Content>
    <Grid Background="Red">
      <TextBlock HorizontalAlignment="Left"
                 Text="Hello, World!" />
    </Grid>
</utu:NavigationBar.Content>

The Content is not stretching properly upon device rotation. So, if you had this NavigationBar setup on a page with an iPad we would start out in Portrait like so:

And rotating to Landscape we then see:

Notice the Red Grid is not properly stretching to adapt to the new NavigationBar width.

Expected behavior would be to see this after rotating to Landscape:

NOTE: If the device starts out with the larger width originally (starting in Landscape), it properly stretches in both orientations:

Starting out in Landscape:

Then rotating to Portrait:

Sample app: NavBarContentTest.zip