Fix build break in VS2017 15.3
@@ -37,7 +37,7 @@ unsigned int TextField::c_borderCornerRadius = 8;
Platform::Boolean TextField::s_dependencyPropertiesRegistered = false;
template <typename T>
-T TextField::FindTemplateChild(FrameworkElement^ source, Platform::String^ name) {
+static T FindTemplateChild(FrameworkElement^ source, Platform::String^ name) {
T target = nullptr;
if (source) {
unsigned int count = VisualTreeHelper::GetChildrenCount(source);
