Throw NoModificationAllowed in SVG*List.removeItem(...) if immutable

Source/core/svg/properties/SVGListPropertyTearOffHelper.h

Index: Source/core/svg/properties/SVGListPropertyTearOffHelper.h
diff --git a/Source/core/svg/properties/SVGListPropertyTearOffHelper.h b/Source/core/svg/properties/SVGListPropertyTearOffHelper.h
index 68fbc99b3544545b7e7f1eabca3f6eb51bf10f97..08e46005a932fc9d9889d49543ebca9dc56f56df 100644
--- a/Source/core/svg/properties/SVGListPropertyTearOffHelper.h
+++ b/Source/core/svg/properties/SVGListPropertyTearOffHelper.h
@@ -162,6 +162,11 @@ public:
 
     PassRefPtrWillBeRawPtr<ItemTearOffType> removeItem(unsigned long index, ExceptionState& exceptionState)
     {
+        if (toDerived()->isImmutable()) {
+            exceptionState.throwDOMException(NoModificationAllowedError, "The object is read-only.");
+            return nullptr;
+        }
+
         RefPtrWillBeRawPtr<ItemPropertyType> value = toDerived()->target()->removeItem(index, exceptionState);
         toDerived()->commitChange();