Added default window size to avoid resizing them to proper size everytime they are run.

samples/BindingTest/BindingTest.csproj

@@ -7,7 +7,8 @@
     <ProjectReference Include="..\..\src\Avalonia.DesignerSupport\Avalonia.DesignerSupport.csproj" />
     
     <ProjectReference Condition="'$(TargetFramework)'=='netcoreapp2.0'"
-     Include="..\..\src\Avalonia.DotNetCoreRuntime\Avalonia.DotNetCoreRuntime.csproj" />
+                      Include="..\..\src\Avalonia.DotNetCoreRuntime\Avalonia.DotNetCoreRuntime.csproj" />
+                      
     <ProjectReference Include="..\..\src\Avalonia.DotNetCoreRuntime\Avalonia.DotNetFrameworkRuntime.csproj" />
 
     <ProjectReference Include="..\..\src\Linux\Avalonia.LinuxFramebuffer\Avalonia.LinuxFramebuffer.csproj" />

samples/BindingTest/MainWindow.xaml

@@ -2,7 +2,9 @@
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
         xmlns:vm="clr-namespace:BindingTest.ViewModels"
         xmlns:local="clr-namespace:BindingTest"
-        Title="AvaloniaUI Bindings Test">
+        Title="AvaloniaUI Bindings Test"
+        Width="800"
+        Height="600">
   <Window.Styles>
     <Style Selector="TextBlock.h1">
       <Setter Property="FontSize" Value="18"/>

samples/RenderTest/MainWindow.xaml

@@ -1,6 +1,8 @@
 <Window xmlns="https://github.com/avaloniaui"
         Title="AvaloniaUI Rendering Test"
-        xmlns:pages="clr-namespace:RenderTest.Pages">
+        xmlns:pages="clr-namespace:RenderTest.Pages"
+        Width="800"
+        Height="600">
   <DockPanel>
     <Menu DockPanel.Dock="Top">
       <MenuItem Header="Rendering">

samples/VirtualizationTest/MainWindow.xaml

@@ -1,5 +1,7 @@
 <Window xmlns="https://github.com/avaloniaui"
-        Title="AvaloniaUI Virtualization Test">
+        Title="AvaloniaUI Virtualization Test"
+        Width="800"
+        Height="600">
     <DockPanel LastChildFill="True" Margin="16">
         <StackPanel DockPanel.Dock="Right" 
                     Margin="16 0 0 0"