Use refs for non-null GraphicsContext, Scrollbar, etc. in scrollbar related code

third_party/WebKit/Source/core/paint/ScrollbarPainter.cpp

 // 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 "config.h"
 #include "core/paint/ScrollbarPainter.h"
 
 #include "core/layout/LayoutScrollbar.h"
 #include "core/layout/LayoutScrollbarPart.h"
 #include "core/paint/BlockPainter.h"
 #include "core/paint/PaintInfo.h"
 #include "platform/graphics/GraphicsContext.h"
 
 namespace blink {
 
-void ScrollbarPainter::paintPart(GraphicsContext* graphicsContext, ScrollbarPart partType, const IntRect& rect)
+void ScrollbarPainter::paintPart(GraphicsContext& graphicsContext, ScrollbarPart partType, const IntRect& rect)
 {
     const LayoutScrollbarPart* partLayoutObject = m_layoutScrollbar->getPart(partType);
     if (!partLayoutObject)
         return;
     paintIntoRect(*partLayoutObject, graphicsContext, m_layoutScrollbar->location(), LayoutRect(rect));
 }
 
-void ScrollbarPainter::paintIntoRect(const LayoutScrollbarPart& layoutScrollbarPart, GraphicsContext* graphicsContext, const LayoutPoint& paintOffset, const LayoutRect& rect)
+void ScrollbarPainter::paintIntoRect(const LayoutScrollbarPart& layoutScrollbarPart, GraphicsContext& graphicsContext, const LayoutPoint& paintOffset, const LayoutRect& rect)
 {
     // Make sure our dimensions match the rect.
     // FIXME: Setting these is a bad layering violation!
     const_cast<LayoutScrollbarPart&>(layoutScrollbarPart).setLocation(rect.location() - toSize(paintOffset));
     const_cast<LayoutScrollbarPart&>(layoutScrollbarPart).setWidth(rect.width());
     const_cast<LayoutScrollbarPart&>(layoutScrollbarPart).setHeight(rect.height());
 
     // Now do the paint.
-    PaintInfo paintInfo(graphicsContext, pixelSnappedIntRect(rect), PaintPhaseBlockBackground, GlobalPaintNormalPhase, PaintLayerNoFlag);
+    PaintInfo paintInfo(&graphicsContext, pixelSnappedIntRect(rect), PaintPhaseBlockBackground, GlobalPaintNormalPhase, PaintLayerNoFlag);
     BlockPainter blockPainter(layoutScrollbarPart);
     blockPainter.paint(paintInfo, paintOffset);
     paintInfo.phase = PaintPhaseChildBlockBackgrounds;
     blockPainter.paint(paintInfo, paintOffset);
     paintInfo.phase = PaintPhaseFloat;
     blockPainter.paint(paintInfo, paintOffset);
     paintInfo.phase = PaintPhaseForeground;
     blockPainter.paint(paintInfo, paintOffset);
     paintInfo.phase = PaintPhaseOutline;
     blockPainter.paint(paintInfo, paintOffset);
 }
 
 } // namespace blink