Use RefPtr to manage shaders in Gradient and Pattern.

Source/core/platform/graphics/Pattern.h

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2007-2008 Torch Mobile, Inc.
  * 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:
  * 1. Redistributions of source code must retain the above copyright
@@ skipping 29 matching lines @@
 namespace WebCore {
 
 class AffineTransform;
 
 class Pattern : public RefCounted<Pattern> {
 public:
     static PassRefPtr<Pattern> create(PassRefPtr<Image> tileImage, bool repeatX, bool repeatY)
     {
         return adoptRef(new Pattern(tileImage, repeatX, repeatY));
     }
-    virtual ~Pattern();
+    ~Pattern();
 
     Image* tileImage() const { return m_tileImage.get(); }
 
     SkShader* shader();
 
     void setPatternSpaceTransform(const AffineTransform& patternSpaceTransformation);
     const AffineTransform& getPatternSpaceTransform() { return m_patternSpaceTransformation; };
 
     bool repeatX() const { return m_repeatX; }
     bool repeatY() const { return m_repeatY; }
 
 private:
     Pattern(PassRefPtr<Image>, bool repeatX, bool repeatY);
 
     RefPtr<Image> m_tileImage;
     bool m_repeatX;
     bool m_repeatY;
     AffineTransform m_patternSpaceTransformation;
-    SkShader* m_pattern;
+    RefPtr<SkShader> m_pattern;
     int m_externalMemoryAllocated;
 };
 
 } //namespace
 
 #endif