Remove SVGElementInstance

Source/core/svg/SVGElement.cpp

Index: Source/core/svg/SVGElement.cpp
diff --git a/Source/core/svg/SVGElement.cpp b/Source/core/svg/SVGElement.cpp
index 7f1904c2b9d4b2db6f74236dd3ac24ed2f8dae74..3a9898fc0694ce2fde8e34a04520741f5d955cd1 100644
--- a/Source/core/svg/SVGElement.cpp
+++ b/Source/core/svg/SVGElement.cpp
@@ -107,6 +107,20 @@ SVGElement::~SVGElement()
 #endif
 }
 
+void SVGElement::detach(const AttachContext& context)
+{
+    Element::detach(context);
+    if (correspondingElement())
+        correspondingElement()->removeInstanceMapping(this);
+}
+
+void SVGElement::attach(const AttachContext& context)
+{
+    Element::attach(context);
+    if (correspondingElement())
+        correspondingElement()->mapInstanceToElement(this);
+}
+
 short SVGElement::tabIndex() const
 {
     if (supportsFocus())
@@ -330,7 +344,7 @@ void SVGElement::childrenChanged(bool changedByParser, Node* beforeChange, Node*
 {
     Element::childrenChanged(changedByParser, beforeChange, afterChange, childCountDelta);
 
-    // Invalidate all SVGElementInstances associated with us.
+    // Invalidate all instances associated with us.
     if (!changedByParser)
         invalidateInstances();
 }
@@ -525,6 +539,9 @@ void SVGElement::removeInstanceMapping(SVGElement* instance)
     ASSERT(instance);
     ASSERT(instance->inUseShadowTree());
 
+    if (!hasSVGRareData())
+        return;
+
     WillBeHeapHashSet<RawPtrWillBeWeakMember<SVGElement> >& instances = svgRareData()->elementInstances();
     ASSERT(instances.contains(instance));
 
@@ -1042,6 +1059,8 @@ void SVGElement::invalidateInstances()
         }
     }
 
+    svgRareData()->elementInstances().clear();
+
     document().updateRenderTreeIfNeeded();
 }