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

third_party/WebKit/public/platform/WebScrollbarThemePainter.h

 /*
  * Copyright (C) 2012 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:
  *
  * 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
@@ skipping 53 matching lines @@
     BLINK_PLATFORM_EXPORT void paintTickmarks(WebCanvas*, const WebRect&);
     BLINK_PLATFORM_EXPORT void paintThumb(WebCanvas*, const WebRect&);
 
     // This opacity is applied on top of the content that is painted for the thumb.
     BLINK_PLATFORM_EXPORT float thumbOpacity() const;
 
     BLINK_PLATFORM_EXPORT bool trackNeedsRepaint() const;
     BLINK_PLATFORM_EXPORT bool thumbNeedsRepaint() const;
 
 #if INSIDE_BLINK
-    BLINK_PLATFORM_EXPORT WebScrollbarThemePainter(ScrollbarTheme*, Scrollbar*, float deviceScaleFactor);
+    BLINK_PLATFORM_EXPORT WebScrollbarThemePainter(ScrollbarTheme&, Scrollbar&, float deviceScaleFactor);
 #endif
 
 private:
     // The theme is not owned by this class. It is assumed that the theme is a
     // static pointer and its lifetime is essentially infinite. The functions
     // called from the painter may not be thread-safe, so all calls must be made
     // from the same thread that it is created on.
     ScrollbarTheme* m_theme;
 
     // It is assumed that the constructor of this paint object is responsible
     // for the lifetime of this scrollbar. The painter has to use the real
     // scrollbar (and not a WebScrollbar wrapper) due to static_casts for
     // LayoutScrollbar and pointer-based HashMap lookups for Lion scrollbars.
     WebPrivatePtr<Scrollbar> m_scrollbar;
 
     float m_deviceScaleFactor;
 };
 
 } // namespace blink
 
 #endif