Take into account memory allocated in XHR for ArrayBuffer.

Source/WebCore/xml/XMLHttpRequest.cpp

@@ -862,6 +862,7 @@ void XMLHttpRequest::clearResponse()
 
 void XMLHttpRequest::clearResponseBuffers()
 {
+    m_reportedExtraMemoryCost = 0;
     m_responseBuilder.clear();
     m_responseEncoding = String();
     m_createdDocument = false;
@@ -907,20 +908,31 @@ void XMLHttpRequest::abortError()
     dispatchErrorEvents(eventNames().abortEvent);
 }
 
-void XMLHttpRequest::dropProtection()
+size_t XMLHttpRequest::extraMemoryCost() const
 {
-    // The XHR object itself holds on to the responseText, and
-    // thus has extra cost even independent of any
-    // responseText or responseXML objects it has handed
-    // out. But it is protected from GC while loading, so this
-    // can't be recouped until the load is done, so only
-    // report the extra cost at that point.
-    JSC::VM& vm = scriptExecutionContext()->vm();
-    JSC::JSLockHolder lock(vm);
-    // FIXME: Adopt reportExtraMemoryVisited, and switch to reportExtraMemoryAllocated.
-    // https://bugs.webkit.org/show_bug.cgi?id=142595
-    vm.heap.deprecatedReportExtraMemory(m_responseBuilder.length() * 2);
+    size_t extraMemoryCost = m_responseBuilder.length();
+    extraMemoryCost += m_binaryResponseBuilder ?  m_binaryResponseBuilder->size() : 0;
+    return extraMemoryCost;
+}
+
+void XMLHttpRequest::reportExtraMemoryCost()
+{
+    size_t extraMemoryCost = this->extraMemoryCost();
+    if (extraMemoryCost < m_reportedExtraMemoryCost)
+        return;
+    size_t extraMemoryCostDelta = extraMemoryCost - m_reportedExtraMemoryCost;
+    if (extraMemoryCostDelta > 0) {
+        JSC::VM& vm = scriptExecutionContext()->vm();
+        JSC::JSLockHolder lock(vm);
+        // FIXME: Adopt reportExtraMemoryVisited, and switch to reportExtraMemoryAllocated.
+        // https://bugs.webkit.org/show_bug.cgi?id=142595
+        vm.heap.deprecatedReportExtraMemory(extraMemoryCostDelta);
+        m_reportedExtraMemoryCost = extraMemoryCost;
+    }
+}
 
+void XMLHttpRequest::dropProtection()
+{
     unsetPendingActivity(this);
 }
 
@@ -1105,6 +1117,8 @@ void XMLHttpRequest::didFinishLoading(unsigned long identifier, double)
 
     m_responseBuilder.shrinkToFit();
 
+    reportExtraMemoryCost();
+
     InspectorInstrumentation::didFinishXHRLoading(scriptExecutionContext(), this, identifier, m_responseBuilder.toStringPreserveCapacity(), m_url, m_lastSendURL, m_lastSendLineNumber, m_lastSendColumnNumber);
 
     bool hadLoader = m_loader;

Source/WebCore/xml/XMLHttpRequest.h

@@ -200,6 +200,10 @@ class XMLHttpRequest final : public ScriptWrappable, public RefCounted<XMLHttpRe
 
     void resumeTimerFired();
 
+    size_t extraMemoryCost() const;
+    void reportExtraMemoryCost();
+    size_t m_reportedExtraMemoryCost;
+
     std::unique_ptr<XMLHttpRequestUpload> m_upload;
 
     URL m_url;