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

third_party/WebKit/Source/core/frame/VisualViewport.cpp

Index: third_party/WebKit/Source/core/frame/VisualViewport.cpp
diff --git a/third_party/WebKit/Source/core/frame/VisualViewport.cpp b/third_party/WebKit/Source/core/frame/VisualViewport.cpp
index c14a23d716f2697cb07e40e05586b09a857e2854..577f983bd17f77e613d0310fbb297e86793411fe 100644
--- a/third_party/WebKit/Source/core/frame/VisualViewport.cpp
+++ b/third_party/WebKit/Source/core/frame/VisualViewport.cpp
@@ -453,10 +453,8 @@
     ASSERT(coordinator);
     ScrollbarOrientation webcoreOrientation =
         isHorizontal ? HorizontalScrollbar : VerticalScrollbar;
-    WebLayer* scrollLayer = layerForScrolling()->platformLayer();
     webScrollbarLayer = coordinator->createSolidColorScrollbarLayer(
-        webcoreOrientation, thumbThickness, scrollbarMargin, false,
-        scrollLayer);
+        webcoreOrientation, thumbThickness, scrollbarMargin, false);
 
     // The compositor will control the scrollbar's visibility. Set to invisible
     // by default so scrollbars don't show up in layout tests.
@@ -485,6 +483,14 @@
   scrollbarGraphicsLayer->setPosition(IntPoint(xPosition, yPosition));
   scrollbarGraphicsLayer->setSize(FloatSize(width, height));
   scrollbarGraphicsLayer->setContentsRect(IntRect(0, 0, width, height));
+}
+
+void VisualViewport::setScrollLayerOnScrollbars(WebLayer* scrollLayer) const {
+  // TODO(bokan): This is currently done while registering viewport layers
+  // with the compositor but could it actually be done earlier, like in
+  // setupScrollbars? Then we wouldn't need this method.
+  m_webOverlayScrollbarHorizontal->setScrollLayer(scrollLayer);
+  m_webOverlayScrollbarVertical->setScrollLayer(scrollLayer);
 }
 
 bool VisualViewport::visualViewportSuppliesScrollbars() const {