Fix tests failing due to previous layout fix.

The test expectations were incorrect after stretch layout with absolute
size fix.

src/Perspex.Controls/Primitives/Thumb.cs

@@ -4,6 +4,7 @@
 using System;
 using Perspex.Input;
 using Perspex.Interactivity;
+using Perspex.Layout;
 
 namespace Perspex.Controls.Primitives
 {

tests/Perspex.Controls.UnitTests/Primitives/TrackTests.cs

@@ -60,6 +60,7 @@ namespace Perspex.Controls.UnitTests.Primitives
                 Orientation = Orientation.Horizontal,
                 Minimum = 100,
                 Maximum = 200,
+                Height = 12,
                 Value = 150,
                 ViewportSize = 50,
             };
@@ -86,6 +87,7 @@ namespace Perspex.Controls.UnitTests.Primitives
                 Maximum = 300,
                 Value = 150,
                 ViewportSize = 50,
+                Width = 12,
             };
 
             target.Measure(new Size(100, 100));
@@ -104,6 +106,7 @@ namespace Perspex.Controls.UnitTests.Primitives
 
             var target = new Track
             {
+                Height = 12,
                 Thumb = thumb,
                 Orientation = Orientation.Horizontal,
                 Minimum = 100,

tests/Perspex.SceneGraph.UnitTests/VisualTree/BoundsTrackerTests.cs

@@ -40,13 +40,13 @@ namespace Perspex.SceneGraph.UnitTests.VisualTree
             var results = new List<TransformedBounds>();
             track.Subscribe(results.Add);
 
-            Assert.Equal(new Rect(15, 15, 15, 15), results.Last().Bounds);
+            Assert.Equal(new Rect(42, 42, 15, 15), results.Last().Bounds);
 
             tree.Padding = new Thickness(15);
             tree.Measure(Size.Infinity);
             tree.Arrange(new Rect(0, 0, 100, 100), true);
 
-            Assert.Equal(new Rect(20, 20, 15, 15), results.Last().Bounds);
+            Assert.Equal(new Rect(42, 42, 15, 15), results.Last().Bounds);
         }
     }
 }