[XHR] Decrease readyStateChange event dispatching during loading.

third_party/WebKit/Source/core/xmlhttprequest/XMLHttpRequest.cpp

 /*
  *  Copyright (C) 2004, 2006, 2008 Apple Inc. All rights reserved.
  *  Copyright (C) 2005-2007 Alexey Proskuryakov <ap@webkit.org>
  *  Copyright (C) 2007, 2008 Julien Chaffraix <jchaffraix@webkit.org>
  *  Copyright (C) 2008, 2011 Google Inc. All rights reserved.
  *  Copyright (C) 2012 Intel Corporation
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
  *  License as published by the Free Software Foundation; either
@@ skipping 470 matching lines @@
 {
     if (!m_upload)
         m_upload = XMLHttpRequestUpload::create(this);
     return m_upload.get();
 }
 
 void XMLHttpRequest::trackProgress(long long length)
 {
     m_receivedLength += length;
 
-    if (m_state != LOADING) {
-        changeState(LOADING);
-    } else {
-        // Dispatch a readystatechange event because many applications use
-        // it to track progress although this is not specified.
-        //
-        // FIXME: Stop dispatching this event for progress tracking.
-        dispatchReadyStateChangeEvent();
+    changeState(LOADING);
+    if (m_async) {
+        // readyStateChange event is fired as well.
+        dispatchProgressEventFromSnapshot(EventTypeNames::progress);
     }
-    if (m_async)
-        dispatchProgressEventFromSnapshot(EventTypeNames::progress);
 }
 
 void XMLHttpRequest::changeState(State newState)
 {
     if (m_state != newState) {
         m_state = newState;
         dispatchReadyStateChangeEvent();
     }
 }
 
 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;
         if (m_state == DONE) {
             if (m_error)
                 action = XMLHttpRequestProgressEventThrottle::Clear;
             else
                 action = XMLHttpRequestProgressEventThrottle::Flush;
         }
@@ skipping 1187 matching lines @@
     visitor->trace(m_responseDocumentParser);
     visitor->trace(m_progressEventThrottle);
     visitor->trace(m_upload);
     visitor->trace(m_blobLoader);
     XMLHttpRequestEventTarget::trace(visitor);
     DocumentParserClient::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink