Bug 1000974 - Don't do cycle collector optimization for nodes in the shadow tree. r=smaug

content/base/src/nsINode.cpp

@@ -1286,7 +1286,8 @@ nsINode::UnoptimizableCCNode() const
   const uintptr_t problematicFlags = (NODE_IS_ANONYMOUS_ROOT |
                                       NODE_IS_IN_NATIVE_ANONYMOUS_SUBTREE |
                                       NODE_IS_NATIVE_ANONYMOUS_ROOT |
-                                      NODE_MAY_BE_IN_BINDING_MNGR);
+                                      NODE_MAY_BE_IN_BINDING_MNGR |
+                                      NODE_IS_IN_SHADOW_TREE);
   return HasFlag(problematicFlags) ||
          NodeType() == nsIDOMNode::ATTRIBUTE_NODE ||
          // For strange cases like xbl:content/xbl:children