Ensure Window.Width/Height is initialized.

- Run resize logic if `Width`/`Height` are still NaN (i.e. not set up)
- Always call base class `WindowBase.HandleResize`
- In `WindowBase.HandleResize` don't run a layout pass if client size unchanged

Fixes `Width_Height_Should_Not_Be_NaN_After_Show_With_SizeToContent_Manual`.

src/Avalonia.Controls/Window.cs

@@ -991,28 +991,28 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         protected sealed override void HandleResized(Size clientSize, PlatformResizeReason reason)
         {
-            if (ClientSize == clientSize)
-                return;
-
-            var sizeToContent = SizeToContent;
-
-            // If auto-sizing is enabled, and the resize came from a user resize (or the reason was
-            // unspecified) then turn off auto-resizing for any window dimension that is not equal
-            // to the requested size.
-            if (sizeToContent != SizeToContent.Manual &&
-                CanResize &&
-                reason == PlatformResizeReason.Unspecified ||  
-                reason == PlatformResizeReason.User)
+            if (ClientSize != clientSize || double.IsNaN(Width) || double.IsNaN(Height))
             {
-                if (clientSize.Width != ClientSize.Width)
-                    sizeToContent &= ~SizeToContent.Width;
-                if (clientSize.Height != ClientSize.Height)
-                    sizeToContent &= ~SizeToContent.Height;
-                SizeToContent = sizeToContent;
-            }
+                var sizeToContent = SizeToContent;
+
+                // If auto-sizing is enabled, and the resize came from a user resize (or the reason was
+                // unspecified) then turn off auto-resizing for any window dimension that is not equal
+                // to the requested size.
+                if (sizeToContent != SizeToContent.Manual &&
+                    CanResize &&
+                    reason == PlatformResizeReason.Unspecified ||
+                    reason == PlatformResizeReason.User)
+                {
+                    if (clientSize.Width != ClientSize.Width)
+                        sizeToContent &= ~SizeToContent.Width;
+                    if (clientSize.Height != ClientSize.Height)
+                        sizeToContent &= ~SizeToContent.Height;
+                    SizeToContent = sizeToContent;
+                }
 
-            Width = clientSize.Width;
-            Height = clientSize.Height;
+                Width = clientSize.Width;
+                Height = clientSize.Height;
+            }
 
             base.HandleResized(clientSize, reason);
         }

src/Avalonia.Controls/WindowBase.cs

@@ -217,10 +217,16 @@ namespace Avalonia.Controls
         /// <param name="reason">The reason for the resize.</param>
         protected override void HandleResized(Size clientSize, PlatformResizeReason reason)
         {
-            ClientSize = clientSize;
             FrameSize = PlatformImpl?.FrameSize;
-            LayoutManager.ExecuteLayoutPass();
-            Renderer?.Resized(clientSize);
+
+            if (ClientSize != clientSize)
+            {
+                ClientSize = clientSize;
+                LayoutManager.ExecuteLayoutPass();
+                Renderer?.Resized(clientSize);
+            }
+
+            System.Diagnostics.Debug.WriteLine($"HandleResized: ClientSize {ClientSize} | FrameSize {FrameSize}");
         }
 
         /// <summary>