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

third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h

 /*
  * Copyright (C) 2011 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 27 matching lines @@
     enum HitTestBehavior { AllowHitTest, DisallowHitTest };
 
     ScrollbarThemeOverlay(int thumbThickness, int scrollbarMargin, HitTestBehavior);
     ScrollbarThemeOverlay(int thumbThickness, int scrollbarMargin, HitTestBehavior, Color);
     ~ScrollbarThemeOverlay() override {}
 
     int scrollbarThickness(ScrollbarControlSize) override;
     int scrollbarMargin() const override;
     bool usesOverlayScrollbars() const override;
 
-    int thumbPosition(const ScrollbarThemeClient*) override;
-    int thumbLength(const ScrollbarThemeClient*) override;
+    int thumbPosition(const ScrollbarThemeClient&) override;
+    int thumbLength(const ScrollbarThemeClient&) override;
 
-    bool hasButtons(const ScrollbarThemeClient*) override { return false; }
-    bool hasThumb(const ScrollbarThemeClient*) override;
+    bool hasButtons(const ScrollbarThemeClient&) override { return false; }
+    bool hasThumb(const ScrollbarThemeClient&) override;
 
-    IntRect backButtonRect(const ScrollbarThemeClient*, ScrollbarPart, bool painting = false) override;
-    IntRect forwardButtonRect(const ScrollbarThemeClient*, ScrollbarPart, bool painting = false) override;
-    IntRect trackRect(const ScrollbarThemeClient*, bool painting = false) override;
-    int thumbThickness(const ScrollbarThemeClient*) override;
+    IntRect backButtonRect(const ScrollbarThemeClient&, ScrollbarPart, bool painting = false) override;
+    IntRect forwardButtonRect(const ScrollbarThemeClient&, ScrollbarPart, bool painting = false) override;
+    IntRect trackRect(const ScrollbarThemeClient&, bool painting = false) override;
+    int thumbThickness(const ScrollbarThemeClient&) override;
+    int thumbThickness() { return m_thumbThickness; }
 
-    void paintThumb(GraphicsContext*, const ScrollbarThemeClient*, const IntRect&) override;
-    ScrollbarPart hitTest(const ScrollbarThemeClient*, const IntPoint&) override;
+    void paintThumb(GraphicsContext&, const ScrollbarThemeClient&, const IntRect&) override;
+    ScrollbarPart hitTest(const ScrollbarThemeClient&, const IntPoint&) override;
 
-    static ScrollbarTheme* mobileTheme();
+    static ScrollbarThemeOverlay& mobileTheme();
 
 private:
     int m_thumbThickness;
     int m_scrollbarMargin;
     HitTestBehavior m_allowHitTest;
     Color m_color;
     const bool m_useSolidColor;
 };
 
 } // namespace blink
 
 #endif