Merge 142759

Source/WebCore/svg/properties/SVGListProperty.h

Index: Source/WebCore/svg/properties/SVGListProperty.h
===================================================================
--- Source/WebCore/svg/properties/SVGListProperty.h	(revision 143529)
+++ Source/WebCore/svg/properties/SVGListProperty.h	(working copy)
@@ -221,7 +221,10 @@
             index = m_values->size();
 
         // Spec: If newItem is already in a list, it is removed from its previous list before it is inserted into this list.
-        processIncomingListItemValue(newItem, &index);
+        if (!processIncomingListItemValue(newItem, &index)) {
+            // Inserting the item before itself is a no-op.
+            return newItem;
+        }
 
         // Spec: Inserts a new item into the list at the specified position. The index of the item before which the new item is to be
         // inserted. The first item is number 0. If the index is equal to 0, then the new item is inserted at the front of the list.
@@ -251,7 +254,8 @@
         ASSERT(m_values->size() == m_wrappers->size());
 
         // Spec: If newItem is already in a list, it is removed from its previous list before it is inserted into this list.
-        processIncomingListItemWrapper(newItem, &index);
+        if (!processIncomingListItemWrapper(newItem, &index))
+            return newItem.release();
 
         // Spec: Inserts a new item into the list at the specified position. The index of the item before which the new item is to be
         // inserted. The first item is number 0. If the index is equal to 0, then the new item is inserted at the front of the list.
@@ -285,7 +289,10 @@
 
         // Spec: If newItem is already in a list, it is removed from its previous list before it is inserted into this list.
         // Spec: If the item is already in this list, note that the index of the item to replace is before the removal of the item.
-        processIncomingListItemValue(newItem, &index);
+        if (!processIncomingListItemValue(newItem, &index)) {
+            // Replacing the item with itself is a no-op.
+            return newItem;
+        }
 
         if (m_values->isEmpty()) {
             // 'newItem' already lived in our list, we removed it, and now we're empty, which means there's nothing to replace.
@@ -317,7 +324,8 @@
 
         // Spec: If newItem is already in a list, it is removed from its previous list before it is inserted into this list.
         // Spec: If the item is already in this list, note that the index of the item to replace is before the removal of the item.
-        processIncomingListItemWrapper(newItem, &index);
+        if (!processIncomingListItemWrapper(newItem, &index))
+            return newItem.release();
 
         if (m_values->isEmpty()) {
             ASSERT(m_wrappers->isEmpty());
@@ -461,8 +469,8 @@
         commitChange();
     }
 
-    virtual void processIncomingListItemValue(const ListItemType& newItem, unsigned* indexToModify) = 0;
-    virtual void processIncomingListItemWrapper(RefPtr<ListItemTearOff>& newItem, unsigned* indexToModify) = 0;
+    virtual bool processIncomingListItemValue(const ListItemType& newItem, unsigned* indexToModify) = 0;
+    virtual bool processIncomingListItemWrapper(RefPtr<ListItemTearOff>& newItem, unsigned* indexToModify) = 0;
 
     SVGPropertyRole m_role;
     bool m_ownsValues;