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

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

 /*
  * Copyright (C) 2004, 2006 Apple Computer, 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 86 matching lines @@
     ScrollableArea* scrollableArea() const { return m_scrollableArea; }
 
     int pressedPos() const { return m_pressedPos; }
 
     virtual void setHoveredPart(ScrollbarPart);
     virtual void setPressedPart(ScrollbarPart);
 
     void setProportion(int visibleSize, int totalSize);
     void setPressedPos(int p) { m_pressedPos = p; }
 
-    void paint(GraphicsContext*, const CullRect&) const final;
+    void paint(GraphicsContext&, const CullRect&) const final;
 
     bool isOverlayScrollbar() const override;
     bool shouldParticipateInHitTesting();
 
     void windowActiveChangedForSnowLeopardOnly();
     bool isWindowActive() const;
 
     bool gestureEvent(const PlatformGestureEvent&);
 
     // These methods are used for platform scrollbars to give :hover feedback.  They will not get called
     // when the mouse went down in a scrollbar, since it is assumed the scrollbar will start
     // grabbing all events in that case anyway.
     void mouseMoved(const PlatformMouseEvent&);
     void mouseEntered();
     void mouseExited();
 
     // Used by some platform scrollbars to know when they've been released from capture.
     void mouseUp(const PlatformMouseEvent&);
     void mouseDown(const PlatformMouseEvent&);
 
-    ScrollbarTheme* theme() const { return m_theme; }
+    ScrollbarTheme& theme() const { return m_theme; }
 
     IntRect convertToContainingWidget(const IntRect&) const override;
     IntRect convertFromContainingWidget(const IntRect&) const override;
 
     IntPoint convertToContainingWidget(const IntPoint&) const override;
     IntPoint convertFromContainingWidget(const IntPoint&) const override;
 
     void moveThumb(int pos, bool draggingDocument = false);
 
     bool isAlphaLocked() const override { return m_isAlphaLocked; }
@@ skipping 31 matching lines @@
     void autoscrollTimerFired(Timer<Scrollbar>*);
     void startTimerIfNeeded(double delay);
     void stopTimerIfNeeded();
     void autoscrollPressedPart(double delay);
     ScrollDirectionPhysical pressedPartScrollDirectionPhysical();
     ScrollGranularity pressedPartScrollGranularity();
 
     RawPtrWillBeMember<ScrollableArea> m_scrollableArea;
     ScrollbarOrientation m_orientation;
     ScrollbarControlSize m_controlSize;
-    ScrollbarTheme* m_theme;
+    ScrollbarTheme& m_theme;
 
     int m_visibleSize;
     int m_totalSize;
     float m_currentPos;
     float m_dragOrigin;
 
     ScrollbarPart m_hoveredPart;
     ScrollbarPart m_pressedPart;
     int m_pressedPos;
     float m_scrollPos;
@@ skipping 19 matching lines @@
 
     bool m_trackNeedsRepaint;
     bool m_thumbNeedsRepaint;
 };
 
 DEFINE_TYPE_CASTS(Scrollbar, Widget, widget, widget->isScrollbar(), widget.isScrollbar());
 
 } // namespace blink
 
 #endif // Scrollbar_h