Protect readystatechange event dispatch on XMLHttpRequest.

Source/core/xmlhttprequest/XMLHttpRequest.cpp

Index: Source/core/xmlhttprequest/XMLHttpRequest.cpp
diff --git a/Source/core/xmlhttprequest/XMLHttpRequest.cpp b/Source/core/xmlhttprequest/XMLHttpRequest.cpp
index 6101b08ca67e94baa691d895d1da4fbbce991c9f..45a7de2e9723d073e909c097917a54a1540198fc 100644
--- a/Source/core/xmlhttprequest/XMLHttpRequest.cpp
+++ b/Source/core/xmlhttprequest/XMLHttpRequest.cpp
@@ -664,6 +664,9 @@ void XMLHttpRequest::dispatchReadyStateChangeEvent()
     if (!executionContext())
         return;
 
+    // We need this protection because dispatchReadyStateChangeEvent may
+    // dispatch multiple events.
+    ScopedEventDispatchProtect protect(&m_eventDispatchRecursionLevel);
     if (m_async || (m_state <= OPENED || m_state == DONE)) {
         TRACE_EVENT1("devtools.timeline", "XHRReadyStateChange", "data", InspectorXhrReadyStateChangeEvent::data(executionContext(), this));
         XMLHttpRequestProgressEventThrottle::DeferredEventAction action = XMLHttpRequestProgressEventThrottle::Ignore;