Get rid of static deferredSetter used for PriorityValues. Use a single DeferredSetter for both styled and direct properties.

src/Avalonia.Base/AvaloniaObject.cs

@@ -22,7 +22,7 @@ namespace Avalonia
     /// <remarks>
     /// This class is analogous to DependencyObject in WPF.
     /// </remarks>
-    public class AvaloniaObject : IAvaloniaObject, IAvaloniaObjectDebug, INotifyPropertyChanged, IPriorityValueOwner
+    public class AvaloniaObject : IAvaloniaObject, IAvaloniaObjectDebug, INotifyPropertyChanged
     {
         /// <summary>
         /// The parent object that inherited values are inherited from.
@@ -414,9 +414,8 @@ namespace Avalonia
             VerifyAccess();
             _values?.Revalidate(property);
         }
-
-        /// <inheritdoc/>
-        void IPriorityValueOwner.Changed(AvaloniaProperty property, int priority, object oldValue, object newValue)
+        
+        internal void PriorityValueChanged(AvaloniaProperty property, int priority, object oldValue, object newValue)
         {
             oldValue = (oldValue == AvaloniaProperty.UnsetValue) ?
                 GetDefaultValue(property) :
@@ -439,9 +438,8 @@ namespace Avalonia
                     (BindingPriority)priority);
             }
         }
-
-        /// <inheritdoc/>
-        void IPriorityValueOwner.BindingNotificationReceived(AvaloniaProperty property, BindingNotification notification)
+        
+        internal void BindingNotificationReceived(AvaloniaProperty property, BindingNotification notification)
         {
             UpdateDataValidation(property, notification);
         }
@@ -566,15 +564,15 @@ namespace Avalonia
             T value)
         {
             Contract.Requires<ArgumentNullException>(setterCallback != null);
-            return DirectPropertyDeferredSetter.SetAndNotify(
+            return _values.Setter.SetAndNotify(
                 property,
                 ref field,
-                (object val, ref T backing, Action<Action> notify) =>
+                ((object value, int) update, ref T backing, Action<Action> notify) =>
                 {
-                    setterCallback((T)val, ref backing, notify);
+                    setterCallback((T)update.value, ref backing, notify);
                     return true;
                 },
-                value);
+                (value, 0));
         }
 
         /// <summary>

src/Avalonia.Base/IPriorityValueOwner.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using Avalonia.Data;
+using Avalonia.Utilities;
 
 namespace Avalonia
 {
@@ -31,5 +32,7 @@ namespace Avalonia
         /// Ensures that the current thread is the UI thread.
         /// </summary>
         void VerifyAccess();
+
+        DeferredSetter<AvaloniaProperty, (object value, int priority)> Setter { get; }
     }
 }

src/Avalonia.Base/PriorityValue.cs

@@ -21,7 +21,7 @@ namespace Avalonia
     /// priority binding that doesn't return <see cref="AvaloniaProperty.UnsetValue"/>. Where there
     /// are multiple bindings registered with the same priority, the most recently added binding
     /// has a higher priority. Each time the value changes, the 
-    /// <see cref="IPriorityValueOwner.Changed(PriorityValue, object, object)"/> method on the 
+    /// <see cref="IPriorityValueOwner.Changed"/> method on the 
     /// owner object is fired with the old and new values.
     /// </remarks>
     internal class PriorityValue
@@ -30,7 +30,6 @@ namespace Avalonia
         private readonly SingleOrDictionary<int, PriorityLevel> _levels = new SingleOrDictionary<int, PriorityLevel>();
 
         private readonly Func<object, object> _validate;
-        private static readonly DeferredSetter<PriorityValue, (object value, int priority)> delayedSetter = new DeferredSetter<PriorityValue, (object, int)>();
         private (object value, int priority) _value;
 
         /// <summary>
@@ -243,7 +242,7 @@ namespace Avalonia
         /// <param name="priority">The priority level that the value came from.</param>
         private void UpdateValue(object value, int priority)
         {
-            delayedSetter.SetAndNotify(this,
+            Owner.Setter.SetAndNotify(Property,
                 ref _value,
                 UpdateCore,
                 (value, priority));
@@ -256,14 +255,13 @@ namespace Avalonia
         {
             var val = update.value;
             var notification = val as BindingNotification;
-            object castValue;
 
             if (notification != null)
             {
                 val = (notification.HasValue) ? notification.Value : null;
             }
 
-            if (TypeUtilities.TryConvertImplicit(_valueType, val, out castValue))
+            if (TypeUtilities.TryConvertImplicit(_valueType, val, out object castValue))
             {
                 var old = backing.value;
 

src/Avalonia.Base/ValueStore.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using Avalonia.Data;
+using Avalonia.Utilities;
 
 namespace Avalonia
 {
@@ -91,12 +92,12 @@ namespace Avalonia
 
         public void BindingNotificationReceived(AvaloniaProperty property, BindingNotification notification)
         {
-            ((IPriorityValueOwner)_owner).BindingNotificationReceived(property, notification);
+            _owner.BindingNotificationReceived(property, notification);
         }
 
         public void Changed(AvaloniaProperty property, int priority, object oldValue, object newValue)
         {
-            ((IPriorityValueOwner)_owner).Changed(property, priority, oldValue, newValue);
+            _owner.PriorityValueChanged(property, priority, oldValue, newValue);
         }
 
         public IDictionary<AvaloniaProperty, PriorityValue> GetSetValues() => throw new NotImplementedException();
@@ -148,13 +149,11 @@ namespace Avalonia
                 validate2 = v => validate(_owner, v);
             }
 
-            PriorityValue result = new PriorityValue(
+            return new PriorityValue(
                 this,
                 property,
                 property.PropertyType,
                 validate2);
-
-            return result;
         }
 
         private object Validate(AvaloniaProperty property, object value)
@@ -168,5 +167,16 @@ namespace Avalonia
 
             return value;
         }
+
+        private DeferredSetter<AvaloniaProperty, (object value, int priority)> _defferedSetter;
+
+        public DeferredSetter<AvaloniaProperty, (object value, int priority)> Setter
+        {
+            get
+            {
+                return _defferedSetter ??
+                    (_defferedSetter = new DeferredSetter<AvaloniaProperty, (object value, int priority)>());
+            }
+        }
     }
 }