Port FlowLayoutPanelDesigner to runtime

src/System.Design/src/System.Design.Forwards.cs

@@ -53,6 +53,7 @@
 [assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.SplitContainerDesigner))]
 [assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.SplitterPanelDesigner))]
 [assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.SplitterDesigner))]
+[assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.FlowLayoutPanelDesigner))]
 [assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.TabControlDesigner))]
 [assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.TableLayoutPanelDesigner))]
 [assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.TabPageDesigner))]

src/System.Windows.Forms.Design/src/System/ComponentModel/Design/ComponentDesigner.cs

@@ -1,6 +1,5 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
 
 #nullable disable
 
@@ -49,6 +48,9 @@ protected bool Inherited
         }
     }
 
+    internal bool IsInheritedReadOnly
+        => InheritanceAttribute.InheritanceLevel == InheritanceLevel.InheritedReadOnly;
+
     /// <summary>
     ///  This property provides a generic mechanism for discovering parent relationships within designers,
     ///  and is used by ComponentDesigner's ITreeDesigner interface implementation.  This property

src/System.Windows.Forms.Design/src/System/ComponentModel/Design/FlowLayoutPanelDesigner.cs

@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Drawing;
+
+namespace System.Windows.Forms.Design;
+
+internal partial class FlowLayoutPanelDesigner
+{
+    private struct ChildInfo
+    {
+        /// <summary>
+        ///  Represents the bounds (including margins) of a child - used for hit testing.
+        /// </summary>
+        public Rectangle MarginBounds;
+
+        /// <summary>
+        ///  Bounds of the control -- used for drawing the IBar.
+        /// </summary>
+        public Rectangle ControlBounds;
+
+        /// <summary>
+        ///  Is this child in the selection collection?
+        /// </summary>
+        public bool InSelectionCollection;
+    }
+}