Add support for setting TrackStart on solid color layers.

cc/layers/solid_color_scrollbar_layer.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/solid_color_scrollbar_layer.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/layers/layer_impl.h"
 #include "cc/layers/solid_color_scrollbar_layer_impl.h"
 
 namespace cc {
 
 scoped_ptr<LayerImpl> SolidColorScrollbarLayer::CreateLayerImpl(
     LayerTreeImpl* tree_impl) {
   const bool kIsOverlayScrollbar = true;
   return SolidColorScrollbarLayerImpl::Create(tree_impl,
                                               id(),
                                               orientation(),
                                               thumb_thickness_,
+                                              track_start_,
                                               is_left_side_vertical_scrollbar_,
                                               kIsOverlayScrollbar)
       .PassAs<LayerImpl>();
 }
 
 scoped_refptr<SolidColorScrollbarLayer> SolidColorScrollbarLayer::Create(
     ScrollbarOrientation orientation,
     int thumb_thickness,
+    int track_start,
     bool is_left_side_vertical_scrollbar,
     int scroll_layer_id) {
-  return make_scoped_refptr(new SolidColorScrollbarLayer(
-      orientation,
-      thumb_thickness,
-      is_left_side_vertical_scrollbar,
-      scroll_layer_id));
+  return make_scoped_refptr(
+      new SolidColorScrollbarLayer(orientation,
+                                   thumb_thickness,
+                                   track_start,
+                                   is_left_side_vertical_scrollbar,
+                                   scroll_layer_id));
 }
 
 SolidColorScrollbarLayer::SolidColorScrollbarLayer(
     ScrollbarOrientation orientation,
     int thumb_thickness,
+    int track_start,
     bool is_left_side_vertical_scrollbar,
     int scroll_layer_id)
     : scroll_layer_id_(Layer::INVALID_ID),
       clip_layer_id_(scroll_layer_id),
       orientation_(orientation),
       thumb_thickness_(thumb_thickness),
+      track_start_(track_start),
       is_left_side_vertical_scrollbar_(is_left_side_vertical_scrollbar) {}
 
 SolidColorScrollbarLayer::~SolidColorScrollbarLayer() {}
 
 ScrollbarLayerInterface* SolidColorScrollbarLayer::ToScrollbarLayer() {
   return this;
 }
 
 void SolidColorScrollbarLayer::PushPropertiesTo(LayerImpl* layer) {
   Layer::PushPropertiesTo(layer);
@@ skipping 34 matching lines @@
 
   clip_layer_id_ = layer_id;
   SetNeedsFullTreeSync();
 }
 
 ScrollbarOrientation SolidColorScrollbarLayer::orientation() const {
   return orientation_;
 }
 
 }  // namespace cc