[CSS Shapes] Add parsing support for gradients

Source/core/rendering/style/ShapeValue.h

 /*
  * Copyright (C) 2012 Adobe Systems Incorporated. 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.
@@ skipping 48 matching lines @@
 
     static PassRefPtr<ShapeValue> createImageValue(PassRefPtr<StyleImage> image)
     {
         return adoptRef(new ShapeValue(image));
     }
 
     ShapeValueType type() const { return m_type; }
     BasicShape* shape() const { return m_shape.get(); }
 
     StyleImage* image() const { return m_image.get(); }
-    bool isImageValid() const { return image() && image()->cachedImage() && image()->cachedImage()->hasImage(); }
+    bool isImageValid() const
+    {
+        if (!image())
+            return false;
+        if (image()->isImageResource() || image()->isImageResourceSet())
+            return image()->cachedImage() && image()->cachedImage()->hasImage();
+        return image()->isGeneratedImage();
+    }
     void setImage(PassRefPtr<StyleImage> image)
     {
         ASSERT(type() == Image);
         if (m_image != image)
             m_image = image;
     }
     CSSBoxType cssBox() const { return m_cssBox; }
 
     bool operator==(const ShapeValue& other) const;
 
@@ skipping 42 matching lines @@
         return image() == other.image();
     }
 
     ASSERT_NOT_REACHED();
     return false;
 }
 
 }
 
 #endif