fontSize has no effect on `<Run>` about react-native-xaml

[asklar]

Good bug. RNW allows view managers to produce FrameworkElement. Run and other things are not FEs, so react-native-xaml fakes this by wrapping it in a ContentControl, and when it is asked to associate a child to its parent, it unwraps the non-FE child and does its magic.
To determine how to set a property, we have a map of property names and a lambda that checks whether the entry is applicable to a certain object or not. This check basically does a cast to check if the object you pass in is of the type that the property is defined in.

fontSize is special in that the property is defined in several types:

{ MAKE_KEY("fontSize"), AsType<winrt::Windows::UI::Xaml::Controls::ContentPresenter>,  []() { return winrt::Windows::UI::Xaml::Controls::ContentPresenter::FontSizeProperty(); }, SetPropValue<double>, ViewManagerPropertyType::Number },
{ MAKE_KEY("fontSize"), AsType<winrt::Windows::UI::Xaml::Controls::Control>,  []() { return winrt::Windows::UI::Xaml::Controls::Control::FontSizeProperty(); }, SetPropValue<double>, ViewManagerPropertyType::Number },
{ MAKE_KEY("fontSize"), AsType<winrt::Windows::UI::Xaml::Controls::FontIcon>,  []() { return winrt::Windows::UI::Xaml::Controls::FontIcon::FontSizeProperty(); }, SetPropValue<double>, ViewManagerPropertyType::Number },
{ MAKE_KEY("fontSize"), AsType<winrt::Windows::UI::Xaml::Controls::RichTextBlock>,  []() { return winrt::Windows::UI::Xaml::Controls::RichTextBlock::FontSizeProperty(); }, SetPropValue<double>, ViewManagerPropertyType::Number },
{ MAKE_KEY("fontSize"), AsType<winrt::Windows::UI::Xaml::Controls::TextBlock>,  []() { return winrt::Windows::UI::Xaml::Controls::TextBlock::FontSizeProperty(); }, SetPropValue<double>, ViewManagerPropertyType::Number },
{ MAKE_KEY("fontSize"), AsUnwrappedType<winrt::Windows::UI::Xaml::Documents::TextElement>,  []() { return winrt::Windows::UI::Xaml::Documents::TextElement::FontSizeProperty(); }, SetPropValue<double>, ViewManagerPropertyType::Number },

What is happening is that we come in with the Run's associated ContentControl wrapper, and we hit the second entry in the table that says "sure, I know how to set a Control's fontSize", and we stop looking.

I think the fix is to re-sort this table by property name first (as it is today), but then sort by specificity (the TextElement cast should come before the Control one)