Setting HeightRequest back to Auto in Xamarin.Forms : <p>In Xamarin.Forms I want to be able to set the exact height for a control whose height is initially determined using VerticalLayoutOptions only (FillAndExpand in this case) and then, at a later point, reset the height of the control back to be automatically determined.</p>

<p>In normal XAML it is possible to do this via double.Nan but performing the following causes an exception to be thrown.:</p>

<pre><code>control.HeightRequest = double.NaN
</code></pre>

<p>How do you set the HeightRequest back to be self-determined?</p>
