Add support for setting TrackStart on solid color layers.

webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc

Index: webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc
diff --git a/webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc b/webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc
index 8d8fd44697f0f19c40c7248ddfb7abb6d84ff522..eabaa4f489efd3bab00752bf121cdd3076412d4f 100644
--- a/webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc
+++ b/webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc
@@ -39,13 +39,14 @@ WebScrollbarLayerImpl::WebScrollbarLayerImpl(
 WebScrollbarLayerImpl::WebScrollbarLayerImpl(
     blink::WebScrollbar::Orientation orientation,
     int thumb_thickness,
+    int track_start,
     bool is_left_side_vertical_scrollbar)
     : layer_(new WebLayerImpl(
-          SolidColorScrollbarLayer::Create(
-              ConvertOrientation(orientation),
-              thumb_thickness,
-              is_left_side_vertical_scrollbar,
-              0))) {}
+          SolidColorScrollbarLayer::Create(ConvertOrientation(orientation),
+                                           thumb_thickness,
+                                           track_start,
+                                           is_left_side_vertical_scrollbar,
+                                           0))) {}
 
 WebScrollbarLayerImpl::~WebScrollbarLayerImpl() {}