Make SVGElement::setCursorImageValue take a const pointer

Fix SVGElement::setCursorImageValue() to take a const
CSSCursorImageValue* instead of just a regular pointer. This is required
pre-work to make StyleBuilderFunctions take const references (since,
when calling into SVGElement::setCursorImageValue from
StyleBuilderFunctions, only a const pointer is available).

BUG=526586

Review-Url: https://codereview.chromium.org/2027113002
Cr-Commit-Position: refs/heads/master@{#397078}

third_party/WebKit/Source/core/svg/SVGElement.cpp

@@ -547,7 +547,7 @@ void SVGElement::setCursorElement(SVGCursorElement* cursorElement)
     rareData->setCursorElement(cursorElement);
 }
 
-void SVGElement::setCursorImageValue(CSSCursorImageValue* cursorImageValue)
+void SVGElement::setCursorImageValue(const CSSCursorImageValue* cursorImageValue)
 {
     ensureSVGRareData()->setCursorImageValue(cursorImageValue);
 }

third_party/WebKit/Source/core/svg/SVGElement.h

@@ -124,7 +124,7 @@ public:
     void removeInstanceMapping(SVGElement*);
 
     void setCursorElement(SVGCursorElement*);
-    void setCursorImageValue(CSSCursorImageValue*);
+    void setCursorImageValue(const CSSCursorImageValue*);
 
     SVGElement* correspondingElement() const;
     void setCorrespondingElement(SVGElement*);

third_party/WebKit/Source/core/svg/SVGElementRareData.h

@@ -64,8 +64,8 @@ public:
     SVGElement* correspondingElement() const { return m_correspondingElement.get(); }
     void setCorrespondingElement(SVGElement* correspondingElement) { m_correspondingElement = correspondingElement; }
 
-    CSSCursorImageValue* cursorImageValue() const { return m_cursorImageValue; }
-    void setCursorImageValue(CSSCursorImageValue* cursorImageValue) { m_cursorImageValue = cursorImageValue; }
+    const CSSCursorImageValue* cursorImageValue() const { return m_cursorImageValue; }
+    void setCursorImageValue(const CSSCursorImageValue* cursorImageValue) { m_cursorImageValue = cursorImageValue; }
 
     void setWebAnimatedAttributesDirty(bool dirty) { m_webAnimatedAttributesDirty = dirty; }
     bool webAnimatedAttributesDirty() const { return m_webAnimatedAttributesDirty; }
@@ -92,7 +92,7 @@ private:
     SVGElementSet m_incomingReferences;
     HeapHashSet<WeakMember<SVGElement>> m_elementInstances;
     WeakMember<SVGCursorElement> m_cursorElement;
-    WeakMember<CSSCursorImageValue> m_cursorImageValue;
+    WeakMember<const CSSCursorImageValue> m_cursorImageValue;
     Member<SVGElement> m_correspondingElement;
     bool m_instancesUpdatesBlocked : 1;
     bool m_useOverrideComputedStyle : 1;