Remove old class, make layout manager private

src/Avalonia.Base/Layout/IEmbeddedLayoutRoot.cs

@@ -1,10 +0,0 @@
-namespace Avalonia.Layout
-{
-    /// <summary>
-    /// A special layout root with enforced size for Arrange pass
-    /// </summary>
-    public interface IEmbeddedLayoutRoot : ILayoutRoot
-    {
-        Size AllocatedSize { get; }
-    }
-}

src/Avalonia.Base/Layout/ILayoutManager.cs

@@ -6,8 +6,7 @@ namespace Avalonia.Layout
     /// <summary>
     /// Manages measuring and arranging of controls.
     /// </summary>
-    [PrivateApi]
-    public interface ILayoutManager : IDisposable
+    internal interface ILayoutManager : IDisposable
     {
         /// <summary>
         /// Raised when the layout manager completes a layout pass.

src/Avalonia.Base/Layout/ILayoutRoot.cs

@@ -5,14 +5,8 @@ namespace Avalonia.Layout
     /// <summary>
     /// Defines the root of a layoutable tree.
     /// </summary>
-    [PrivateApi]
-    public interface ILayoutRoot
+    internal interface ILayoutRoot
     {
-        /// <summary>
-        /// The size available to lay out the controls.
-        /// </summary>
-        Size ClientSize { get; }
-
         /// <summary>
         /// The scaling factor to use in layout.
         /// </summary>

src/Avalonia.Base/Layout/LayoutManager.cs

@@ -17,8 +17,7 @@ namespace Avalonia.Layout
     /// <summary>
     /// Manages measuring and arranging of controls.
     /// </summary>
-    [PrivateApi]
-    public class LayoutManager : ILayoutManager, IDisposable
+    internal class LayoutManager : ILayoutManager, IDisposable
     {
         private const int MaxPasses = 10;
         private readonly Layoutable _owner;
@@ -329,9 +328,7 @@ namespace Avalonia.Layout
 
             if (!control.IsArrangeValid)
             {
-                if (control is IEmbeddedLayoutRoot embeddedRoot)
-                    control.Arrange(new Rect(embeddedRoot.AllocatedSize));
-                else if (control is ILayoutRoot root)
+                if (control is ILayoutRoot root)
                     control.Arrange(new Rect(control.DesiredSize));
                 else if (control.PreviousArrange != null)
                 {