Revert "Fix scrollviewer causing lockups."

This reverts commit 18e3900edc.

Perspex.Controls/ScrollViewer.cs

@@ -10,7 +10,6 @@ namespace Perspex.Controls
     using System.Reactive.Linq;
     using Perspex.Controls.Presenters;
     using Perspex.Controls.Primitives;
-    using Perspex.Threading;
 
     public class ScrollViewer : ContentControl
     {
@@ -63,8 +62,7 @@ namespace Perspex.Controls
             var extentAndViewport = Observable.CombineLatest(
                 this.GetObservable(ExtentProperty),
                 this.GetObservable(ViewportProperty))
-                .Select(x => new { Extent = x[0], Viewport = x[1] })
-                .Throttle(TimeSpan.FromMilliseconds(100), PerspexScheduler.Instance);
+                .Select(x => new { Extent = x[0], Viewport = x[1] });
 
             this.Bind(
                 VerticalScrollBarViewportSizeProperty,

Perspex.Diagnostics/DevTools.cs

@@ -118,8 +118,10 @@ namespace Perspex.Diagnostics
             {
                 Window window = new Window
                 {
-                    Width = 1024,
-                    Height = 512,
+                    // HACK: Set width and height here as a quick fix as there's a problem with 
+                    // the dev tools window hanging when it's set to auto-size.
+                    Width = 800,
+                    Height = 600,
                     Content = new DevTools
                     {
                         Root = (Window)sender,