Simplified the scrollbar slider definition.

Bin/Data/UI/DefaultStyle.xml

@@ -125,13 +125,6 @@
         </element>
         <element type="Slider" internal="true">
             <attribute name="Size" value="12 12" />
-            <attribute name="Image Rect" value="48 0 64 16" />
-            <attribute name="Border" value="4 4 4 4" />
-            <element type="BorderImage" internal="true">
-                <attribute name="Image Rect" value="16 0 32 16" />
-                <attribute name="Border" value="4 4 4 4" />
-                <attribute name="Hover Image Offset" value="0 16" />
-            </element>
         </element>
         <element type="Button" internal="true">
             <attribute name="Size" value="12 12" />