Revert of Remove indirection: setup scrollbar scroll layers in the scrollbar constructor

cc/blink/web_scrollbar_layer_impl.cc

Index: cc/blink/web_scrollbar_layer_impl.cc
diff --git a/cc/blink/web_scrollbar_layer_impl.cc b/cc/blink/web_scrollbar_layer_impl.cc
index 4ced75af721953faf294ae090859bdb83383f34f..b6a759c51471a71433c6a424f18107ad89a7f368 100644
--- a/cc/blink/web_scrollbar_layer_impl.cc
+++ b/cc/blink/web_scrollbar_layer_impl.cc
@@ -34,35 +34,35 @@
 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 is_overlay,
-    blink::WebLayer* scroll_layer)
-    : layer_(
-          is_overlay
-              ? new WebLayerImpl(PaintedOverlayScrollbarLayer::Create(
-                    base::MakeUnique<ScrollbarImpl>(std::move(scrollbar),
-                                                    painter,
-                                                    std::move(geometry)),
-                    static_cast<WebLayerImpl*>(scroll_layer)->layer()->id()))
-              : new WebLayerImpl(PaintedScrollbarLayer::Create(
-                    base::MakeUnique<ScrollbarImpl>(std::move(scrollbar),
-                                                    painter,
-                                                    std::move(geometry)),
-                    static_cast<WebLayerImpl*>(scroll_layer)->layer()->id()))) {
-}
+    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,
-    blink::WebLayer* scroll_layer)
-    : layer_(new WebLayerImpl(SolidColorScrollbarLayer::Create(
-          ConvertOrientation(orientation),
-          thumb_thickness,
-          track_start,
-          is_left_side_vertical_scrollbar,
-          static_cast<WebLayerImpl*>(scroll_layer)->layer()->id()))) {}
+    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() {
 }
@@ -71,4 +71,11 @@
   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