Use nine-patch resource for drawing Aura overlay scrollbar thumb.

cc/blink/web_scrollbar_layer_impl.cc

 // Copyright 2014 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/blink/web_scrollbar_layer_impl.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "cc/blink/scrollbar_impl.h"
 #include "cc/blink/web_layer_impl.h"
 #include "cc/layers/layer.h"
+#include "cc/layers/painted_overlay_scrollbar_layer.h"
 #include "cc/layers/painted_scrollbar_layer.h"
 #include "cc/layers/scrollbar_layer_interface.h"
 #include "cc/layers/solid_color_scrollbar_layer.h"
 
+using cc::PaintedOverlayScrollbarLayer;
 using cc::PaintedScrollbarLayer;
 using cc::SolidColorScrollbarLayer;
 
 namespace {
 
 cc::ScrollbarOrientation ConvertOrientation(
     blink::WebScrollbar::Orientation orientation) {
   return orientation == blink::WebScrollbar::Horizontal ? cc::HORIZONTAL
                                                         : cc::VERTICAL;
 }
 
 }  // namespace
 
 namespace cc_blink {
 
 WebScrollbarLayerImpl::WebScrollbarLayerImpl(
     std::unique_ptr<blink::WebScrollbar> scrollbar,
     blink::WebScrollbarThemePainter painter,
     std::unique_ptr<blink::WebScrollbarThemeGeometry> geometry)
     : layer_(new WebLayerImpl(PaintedScrollbarLayer::Create(
           base::MakeUnique<ScrollbarImpl>(std::move(scrollbar),
                                           painter,
                                           std::move(geometry)),
           0))) {}
 
 WebScrollbarLayerImpl::WebScrollbarLayerImpl(
+    std::unique_ptr<blink::WebScrollbar> scrollbar,
+    blink::WebScrollbarThemePainter painter,
+    std::unique_ptr<blink::WebScrollbarThemeGeometry> geometry,
+    bool)
+    : layer_(new WebLayerImpl(PaintedOverlayScrollbarLayer::Create(
+          base::MakeUnique<ScrollbarImpl>(std::move(scrollbar),
+                                          painter,
+                                          std::move(geometry)),
+          0))) {}
+
+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,
                                            track_start,
                                            is_left_side_vertical_scrollbar,
                                            0))) {}
 
 WebScrollbarLayerImpl::~WebScrollbarLayerImpl() {
 }
 
 blink::WebLayer* WebScrollbarLayerImpl::layer() {
   return layer_.get();
 }
 
 void WebScrollbarLayerImpl::setScrollLayer(blink::WebLayer* layer) {
   cc::Layer* scroll_layer =
       layer ? static_cast<WebLayerImpl*>(layer)->layer() : 0;
   layer_->layer()->ToScrollbarLayer()->SetScrollLayer(
       scroll_layer ? scroll_layer->id() : cc::Layer::INVALID_ID);
 }
 
 }  // namespace cc_blink