Protect XHR's wrapper while dispatching event.

Source/core/xmlhttprequest/XMLHttpRequest.h

Index: Source/core/xmlhttprequest/XMLHttpRequest.h
diff --git a/Source/core/xmlhttprequest/XMLHttpRequest.h b/Source/core/xmlhttprequest/XMLHttpRequest.h
index 57ad7803861814556c3408255f8b2f68024ffd8f..10a6dc63d2f25c40afd9092406e355bdc1b26ffd 100644
--- a/Source/core/xmlhttprequest/XMLHttpRequest.h
+++ b/Source/core/xmlhttprequest/XMLHttpRequest.h
@@ -295,6 +295,11 @@ private:
     // |m_responseTypeCode| is NOT ResponseTypeBlob.
     OwnPtrWillBeMember<BlobLoader> m_blobLoader;
 
+    // Positive if we are dispatching events.
+    // This is an integer specifying the recursion level rather than a boolean
+    // because in some cases we have recursive dispatching.
+    int m_eventDispatchRecursionLevel;
+
     bool m_async;
     bool m_includeCredentials;
     // Used to skip m_responseDocument creation if it's done previously. We need