Merge branch '3.5.0'

diff --cc Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
Simple merge

diff --cc Xamarin.Forms.Core/XmlnsDefinitionAttribute.cs
index 295e906,58e80cc..5c27d41
--- 1/Xamarin.Forms.Core/XmlnsDefinitionAttribute.cs
--- 2/Xamarin.Forms.Core/XmlnsDefinitionAttribute.cs
+++ b/Xamarin.Forms.Core/XmlnsDefinitionAttribute.cs
@@@ -20,13 -21,8 +20,8 @@@ namespace Xamarin.Form
  
                public XmlnsDefinitionAttribute(string xmlNamespace, string clrNamespace)
                {
-                       if (xmlNamespace == null)
-                               throw new ArgumentNullException(nameof(xmlNamespace));
-                       if (clrNamespace == null)
-                               throw new ArgumentNullException(nameof(clrNamespace));
- 
-                       ClrNamespace = clrNamespace;
-                       XmlNamespace = xmlNamespace;
+                       ClrNamespace = clrNamespace ?? throw new ArgumentNullException(nameof(xmlNamespace));
+                       XmlNamespace = xmlNamespace ?? throw new ArgumentNullException(nameof(clrNamespace));
                }
        }
 -}
 +}