Fixed problem with DropDown.

samples/XamlTestApplicationPcl/DropDown.paml

@@ -10,7 +10,7 @@
                 BorderBrush="{TemplateBinding BorderBrush}"
                 BorderThickness="{TemplateBinding BorderThickness}">
           <Grid ColumnDefinitions="*,Auto">
-            <ContentPresenter Content="{TemplateBinding Content}"
+            <ContentPresenter Content="{TemplateBinding SelectionBoxItem}"
                               Margin="{TemplateBinding Padding}"
                               HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                               VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>