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

third_party/WebKit/Source/platform/exported/WebScrollbarThemeGeometryNative.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 20 matching lines @@
 #include "public/platform/WebScrollbarThemeGeometry.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace blink {
 
 class ScrollbarTheme;
 class WebScrollbar;
 
 class PLATFORM_EXPORT WebScrollbarThemeGeometryNative : public WebScrollbarThemeGeometry {
 public:
-    static PassOwnPtr<WebScrollbarThemeGeometryNative> create(ScrollbarTheme*);
+    static PassOwnPtr<WebScrollbarThemeGeometryNative> create(ScrollbarTheme&);
 
     // WebScrollbarThemeGeometry overrides
     WebScrollbarThemeGeometryNative* clone() const override;
     int thumbPosition(WebScrollbar*) override;
     int thumbLength(WebScrollbar*) override;
     int trackPosition(WebScrollbar*) override;
     int trackLength(WebScrollbar*) override;
     bool hasButtons(WebScrollbar*) override;
     bool hasThumb(WebScrollbar*) override;
     WebRect trackRect(WebScrollbar*) override;
     WebRect thumbRect(WebScrollbar*) override;
     int minimumThumbLength(WebScrollbar*) override;
     int scrollbarThickness(WebScrollbar*) override;
     WebRect backButtonStartRect(WebScrollbar*) override;
     WebRect backButtonEndRect(WebScrollbar*) override;
     WebRect forwardButtonStartRect(WebScrollbar*) override;
     WebRect forwardButtonEndRect(WebScrollbar*) override;
     WebRect constrainTrackRectToTrackPieces(WebScrollbar*, const WebRect&) override;
     void splitTrack(WebScrollbar*, const WebRect& track, WebRect& startTrack, WebRect& thumb, WebRect& endTrack) override;
 
 private:
-    explicit WebScrollbarThemeGeometryNative(ScrollbarTheme*);
+    explicit WebScrollbarThemeGeometryNative(ScrollbarTheme&);
 
     // The theme is not owned by this class. It is assumed that the theme is a
     // static pointer and its lifetime is essentially infinite. Only thread-safe
     // functions on the theme can be called by this theme.
-    ScrollbarTheme* m_theme;
+    ScrollbarTheme& m_theme;
 };
 
 } // namespace blink
 
 #endif