Prevent crash due to XMLDocumentParser destruction

Source/core/xml/parser/XMLDocumentParser.cpp

Index: Source/core/xml/parser/XMLDocumentParser.cpp
diff --git a/Source/core/xml/parser/XMLDocumentParser.cpp b/Source/core/xml/parser/XMLDocumentParser.cpp
index 26f839d28cde255669a90781a13101210d401d3f..a06e969bb2268ae7687e4797e8b9355e8bd25933 100644
--- a/Source/core/xml/parser/XMLDocumentParser.cpp
+++ b/Source/core/xml/parser/XMLDocumentParser.cpp
@@ -350,6 +350,10 @@ void XMLDocumentParser::append(PassRefPtr<StringImpl> inputSource)
         return;
     }
 
+    // JavaScript can detach the parser. Make sure this is not released
+    // before the end of this method.
+    RefPtr<XMLDocumentParser> protect(this);
+
     doWrite(source.toString());
 
     if (isStopped())