Move Image ownership out of CSSValue

Source/core/style/ComputedStyle.h

Index: Source/core/style/ComputedStyle.h
diff --git a/Source/core/style/ComputedStyle.h b/Source/core/style/ComputedStyle.h
index a52eabc06ef1b7b06dd4ff4666441073408d3f64..3b6f5b6b32907612867a66c8379ca1b8c0329cb4 100644
--- a/Source/core/style/ComputedStyle.h
+++ b/Source/core/style/ComputedStyle.h
@@ -49,6 +49,7 @@
 #include "core/style/StyleFlexibleBoxData.h"
 #include "core/style/StyleGridData.h"
 #include "core/style/StyleGridItemData.h"
+#include "core/style/StyleImage.h"
 #include "core/style/StyleInheritedData.h"
 #include "core/style/StyleMotionPath.h"
 #include "core/style/StyleMultiColData.h"
@@ -148,6 +149,7 @@ protected:
     DataRef<StyleBackgroundData> m_background;
     DataRef<StyleSurroundData> surround;
     DataRef<StyleRareNonInheritedData> rareNonInheritedData;
+    CSSStyleImageMap m_cssImages;
 
     // inherited attributes
     DataRef<StyleRareInheritedData> rareInheritedData;
@@ -381,6 +383,9 @@ public:
 
     const PseudoStyleCache* cachedPseudoStyles() const { return m_cachedPseudoStyles.get(); }
 
+    CSSStyleImageMap& mutableCssImages() { return m_cssImages; }
+    const CSSStyleImageMap& cssImages() const { return m_cssImages; }
+
     void setHasViewportUnits(bool hasViewportUnits = true) const { noninherited_flags.hasViewportUnits = hasViewportUnits; }
     bool hasViewportUnits() const { return noninherited_flags.hasViewportUnits; }