Factor painting code from RenderLayerScrollableArea into ScrollableAreaPainter

Source/core/paint/BlockPainter.cpp

Index: Source/core/paint/BlockPainter.cpp
diff --git a/Source/core/paint/BlockPainter.cpp b/Source/core/paint/BlockPainter.cpp
index d3ed80a33d68337ff6c7d4b617e9921d0a8811b8..809f8ba106cf29a26706314efc9060c4a52080ff 100644
--- a/Source/core/paint/BlockPainter.cpp
+++ b/Source/core/paint/BlockPainter.cpp
@@ -15,6 +15,7 @@
 #include "core/paint/InlinePainter.h"
 #include "core/paint/LineBoxListPainter.h"
 #include "core/paint/RenderDrawingRecorder.h"
+#include "core/paint/ScrollableAreaPainter.h"
 #include "core/rendering/GraphicsContextAnnotator.h"
 #include "core/rendering/PaintInfo.h"
 #include "core/rendering/RenderBlock.h"
@@ -87,7 +88,7 @@ void BlockPainter::paintOverflowControlsIfNeeded(const PaintInfo& paintInfo, con
     PaintPhase phase = paintInfo.phase;
     if (m_renderBlock.hasOverflowClip() && m_renderBlock.style()->visibility() == VISIBLE && (phase == PaintPhaseBlockBackground || phase == PaintPhaseChildBlockBackground) && paintInfo.shouldPaintWithinRoot(&m_renderBlock) && !paintInfo.paintRootBackgroundOnly()) {
         RenderDrawingRecorder recorder(paintInfo.context, &m_renderBlock, paintInfo.phase, pixelSnappedIntRect(paintOffset, m_renderBlock.visualOverflowRect().size()));
-        m_renderBlock.layer()->scrollableArea()->paintOverflowControls(paintInfo.context, roundedIntPoint(paintOffset), paintInfo.rect, false /* paintingOverlayControls */);
+        ScrollableAreaPainter(*m_renderBlock.layer()->scrollableArea()).paintOverflowControls(paintInfo.context, roundedIntPoint(paintOffset), paintInfo.rect, false /* paintingOverlayControls */);
     }
 }