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

Source/core/svg/properties/SVGListPropertyTearOffHelper.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 144 matching lines @@
     }
 
     bool anonymousIndexedSetter(unsigned index, PassRefPtrWillBeRawPtr<ItemTearOffType> passItem, ExceptionState& exceptionState)
     {
         replaceItem(passItem, index, exceptionState);
         return true;
     }
 
     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();
 
         return createItemTearOff(value.release());
     }
 
     PassRefPtrWillBeRawPtr<ItemTearOffType> appendItem(PassRefPtrWillBeRawPtr<ItemTearOffType> passItem, ExceptionState& exceptionState)
     {
         RefPtrWillBeRawPtr<ItemTearOffType> item = passItem;
 
@@ skipping 32 matching lines @@
         return ItemTraits::createTearOff(value, 0, PropertyIsNotAnimVal, QualifiedName::null());
     }
 
 private:
     Derived* toDerived() { return static_cast<Derived*>(this); }
 };
 
 }
 
 #endif // SVGListPropertyTearOffHelper_h