Implement interfaces in PaintInfo and make it a class.

Source/core/platform/graphics/GraphicsContextAnnotation.h

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 18 matching lines @@
  */
 
 #include "wtf/Vector.h"
 #include "wtf/text/WTFString.h"
 
 #ifndef GraphicsContextAnnotation_h
 #define GraphicsContextAnnotation_h
 
 #define ANNOTATE_GRAPHICS_CONTEXT(paintInfo, renderer) \
     GraphicsContextAnnotator scopedGraphicsContextAnnotator; \
-    if (UNLIKELY(paintInfo.context->annotationMode())) \
+    if (UNLIKELY(paintInfo.getContext()->annotationMode()))             \
         scopedGraphicsContextAnnotator.annotate(paintInfo, renderer)
 
 namespace WebCore {
 
 class GraphicsContext;
+class PaintInfo;
 class RenderObject;
-struct PaintInfo;
 
 enum AnnotationMode {
     AnnotateRendererName    = 1 << 0,
     AnnotatePaintPhase      = 1 << 1,
     AnnotateElementId       = 1 << 2,
     AnnotateElementClass    = 1 << 3,
     AnnotateElementTag      = 1 << 4,
 
     AnnotateAll             = 0x1f
 };
 
 typedef unsigned AnnotationModeFlags;
 typedef Vector<std::pair<const char*, String> > AnnotationList;
 
 class GraphicsContextAnnotation {
 public:
-    GraphicsContextAnnotation(const PaintInfo&, const RenderObject*);
+    GraphicsContextAnnotation(PaintInfo&, const RenderObject*);

[do-not-use, 2013/08/05 11:16:30]

I guess we could have 2 context getters so that we can keep the const here:
GraphicsContext* context() { return m_context; }
const GraphicsContext* context() const { return m_context; }

 
     String rendererName() const { return ASCIILiteral(m_rendererName); }
     String paintPhase() const { return ASCIILiteral(m_paintPhase); }
     String elementId() const { return m_elementId; }
     String elementClass() const { return m_elementClass; }
     String elementTag() const { return m_elementTag; }
 
     void asAnnotationList(AnnotationList&) const;
 
 private:
     const char* m_rendererName;
     const char* m_paintPhase;
     String m_elementId;
     String m_elementClass;
     String m_elementTag;
 };
 
 class GraphicsContextAnnotator {
 public:
     GraphicsContextAnnotator()
         : m_context(0)
     { }
 
     ~GraphicsContextAnnotator()
     {
         if (UNLIKELY(m_context != 0))
             finishAnnotation();
     }
 
-    void annotate(const PaintInfo&, const RenderObject*);
+    void annotate(PaintInfo&, const RenderObject*);
 
 private:
     void finishAnnotation();
 
     GraphicsContext* m_context;
 };
 
 } // namespace WebCore
 
 #endif // GraphicsContextAnnotation_h