Implement interfaces in PaintInfo and make it a class.

Source/core/rendering/RenderScrollbarPart.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 168 matching lines @@
     setLocation(rect.location() - toSize(paintOffset));
     setWidth(rect.width());
     setHeight(rect.height());
 
     if (graphicsContext->paintingDisabled())
         return;
 
     // Now do the paint.
     PaintInfo paintInfo(graphicsContext, pixelSnappedIntRect(rect), PaintPhaseBlockBackground, PaintBehaviorNormal);
     paint(paintInfo, paintOffset);
-    paintInfo.phase = PaintPhaseChildBlockBackgrounds;
+    paintInfo.setPhase(PaintPhaseChildBlockBackgrounds);
     paint(paintInfo, paintOffset);
-    paintInfo.phase = PaintPhaseFloat;
+    paintInfo.setPhase(PaintPhaseFloat);
     paint(paintInfo, paintOffset);
-    paintInfo.phase = PaintPhaseForeground;
+    paintInfo.setPhase(PaintPhaseForeground);
     paint(paintInfo, paintOffset);
-    paintInfo.phase = PaintPhaseOutline;
+    paintInfo.setPhase(PaintPhaseOutline);
     paint(paintInfo, paintOffset);
 }
 
 RenderObject* RenderScrollbarPart::rendererOwningScrollbar() const
 {
     if (!m_scrollbar)
         return 0;
     return m_scrollbar->owningRenderer();
 }
 
 }