[SVG] Implement 'discard' element

Source/core/svg/SVGDiscardElement.h

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+ */
+
+#ifndef SVGDiscardElement_h
+#define SVGDiscardElement_h
+
+#include "core/svg/animation/SVGSMILElement.h"
+
+namespace WebCore {
+
+class SVGDiscardElement FINAL : public SVGSMILElement {
+public:
+    static PassRefPtr<SVGDiscardElement> create(Document&);
+
+private:
+    explicit SVGDiscardElement(Document&);
+
+    virtual bool isAdditive() const { return false; }
+    virtual void resetAnimatedType() { }
+    virtual void clearAnimatedType(SVGElement* targetElement) { }
+    virtual void applyResultsToTarget() { }
+    virtual bool hasValidAttributeType();
+    virtual bool hasValidAttributeName() OVERRIDE;
+    virtual void animationAttributeChanged() { }
+
+    virtual void startedActiveInterval() { }
+    virtual void updateAnimation(float percent, unsigned repeat, SVGSMILElement* resultElement) { }
+};
+
+inline bool isSVGDiscardElement(const Node& node)

[pdr., 2013/12/20 23:49:11]

Because this is called for every animation element on every frame, we should try
to make it fast.

Please define this on SVGSMILElement.h:
virtual bool isSVGDiscardElement() const { return false; } 

And add this to SVGDiscardElement.h:
virtual bool isSVGDiscardElement() const OVERRIDE FINAL { return true; } 

+{
+    return node.hasTagName((SVGNames::discardTag));
+}
+
+DEFINE_NODE_TYPE_CASTS_WITH_FUNCTION(SVGDiscardElement);
+
+} // namespace WebCore
+
+#endif // SVGDiscardElement_h