start of CPSplitView theming

AppKit/CPSplitView.j

@@ -61,6 +61,17 @@ var CPSplitViewHorizontalImage = nil,
     CPArray     _buttonBars;
 }
 
++ (CPString)themeClass
+{
+    return @"splitview";
+}
+
++ (id)themeAttributes
+{
+    return [CPDictionary dictionaryWithObjects:[10.0, 1.0]
+                                       forKeys:[@"divider-thickness", @"pane-divider-thickness"]];
+}
+
 /*
     @ignore
 */
@@ -91,7 +102,7 @@ var CPSplitViewHorizontalImage = nil,
 
 - (float)dividerThickness
 {
-    return _isPaneSplitter ? 1.0 : 10.0;
+    return [self currentValueForThemeAttribute:[self isPaneSplitter] ? @"pane-divider-thickness" : @"divider-thickness"];
 }
 
 - (BOOL)isVertical

AppKit/Themes/Aristo/ThemeDescriptors.j

@@ -1333,6 +1333,14 @@ var themedButtonValues = nil,
     return view;
 }
 
++ (CPSplitView)themedSplitView
+{
+    var splitView = [[CPSplitView alloc] initWithFrame:CGRectMake(0.0, 0.0, 200.0, 200.0)];
+    [splitView setValue:10.0 forThemeAttribute:@"divider-thickness"];
+    [splitView setValue:1.0 forThemeAttribute:@"pane-divider-thickness"];
+    return splitView;
+}
+
 + (CPAlert)themedAlert
 {
     var alert = [CPAlert new],