Added tooltip to default theme.

src/Perspex.Themes.Default/DefaultTheme.paml

@@ -23,6 +23,7 @@
   <StyleInclude Source="resource://application/Perspex.Themes.Default/Perspex.Themes.Default.TabStrip.paml"/>
   <StyleInclude Source="resource://application/Perspex.Themes.Default/Perspex.Themes.Default.TextBox.paml"/>
   <StyleInclude Source="resource://application/Perspex.Themes.Default/Perspex.Themes.Default.ToggleButton.paml"/>
+  <StyleInclude Source="resource://application/Perspex.Themes.Default/Perspex.Themes.Default.ToolTip.paml"/>
   <StyleInclude Source="resource://application/Perspex.Themes.Default/Perspex.Themes.Default.TreeView.paml"/>
   <StyleInclude Source="resource://application/Perspex.Themes.Default/Perspex.Themes.Default.TreeViewItem.paml"/>
   <StyleInclude Source="resource://application/Perspex.Themes.Default/Perspex.Themes.Default.Window.paml"/>

src/Perspex.Themes.Default/Perspex.Themes.Default.csproj

@@ -140,6 +140,9 @@
     <EmbeddedResource Include="ProgressBar.paml">
       <SubType>Designer</SubType>
     </EmbeddedResource>
+    <EmbeddedResource Include="ToolTip.paml">
+      <SubType>Designer</SubType>
+    </EmbeddedResource>
     <None Include="packages.config" />
     <EmbeddedResource Include="PopupRoot.paml">
       <SubType>Designer</SubType>

src/Perspex.Themes.Default/ToolTip.paml

@@ -0,0 +1,16 @@
+<Style xmlns="https://github.com/perspex" Selector="ToolTip">
+  <Setter Property="BorderBrush" Value="Gray"/>
+  <Setter Property="BorderThickness" Value="1"/>
+  <Setter Property="Padding" Value="4,2"/>
+  <Setter Property="Template">
+    <ControlTemplate>
+      <Border Background="{TemplateBinding Background}"
+              BorderBrush="{TemplateBinding BorderBrush}"
+              BorderThickness="{TemplateBinding BorderThickness}">
+        <ContentPresenter Name="PART_ContentPresenter" 
+                          Content="{TemplateBinding Content}" 
+                          Margin="{TemplateBinding Padding}"/>
+      </Border>
+    </ControlTemplate>
+  </Setter>
+</Style>