Sync the XHR-related interfaces with the spec

Source/core/events/ProgressEvent.cpp

Index: Source/core/events/ProgressEvent.cpp
diff --git a/Source/core/events/ProgressEvent.cpp b/Source/core/events/ProgressEvent.cpp
index 3d9d5ffc3c2985b84c125748df0ef8ea45236107..55e2f74b43a35d5c5f28a15d8c6496e42a416366 100644
--- a/Source/core/events/ProgressEvent.cpp
+++ b/Source/core/events/ProgressEvent.cpp
@@ -37,16 +37,10 @@ ProgressEvent::ProgressEvent()
 
 ProgressEvent::ProgressEvent(const AtomicString& type, const ProgressEventInit& initializer)
     : Event(type, initializer)
-    , m_lengthComputable(false)
-    , m_loaded(0)
-    , m_total(0)
+    , m_lengthComputable(initializer.lengthComputable())
+    , m_loaded(initializer.loaded())
+    , m_total(initializer.total())
 {
-    if (initializer.hasLengthComputable())
-        m_lengthComputable = initializer.lengthComputable();
-    if (initializer.hasLoaded())
-        m_loaded = initializer.loaded();
-    if (initializer.hasTotal())
-        m_total = initializer.total();
 }
 
 ProgressEvent::ProgressEvent(const AtomicString& type, bool lengthComputable, unsigned long long loaded, unsigned long long total)