Fix XMLHttpRequest leak document when send() is called multiple times.

Source/core/xml/XMLHttpRequest.h

Index: Source/core/xml/XMLHttpRequest.h
diff --git a/Source/core/xml/XMLHttpRequest.h b/Source/core/xml/XMLHttpRequest.h
index a4316f1cdbe2d7954f81735a88fbb02f9bc5c82a..9858ea38ba083e4eac871b95f53beae5cf3c6340 100644
--- a/Source/core/xml/XMLHttpRequest.h
+++ b/Source/core/xml/XMLHttpRequest.h
@@ -74,6 +74,11 @@ public:
         ResponseTypeArrayBuffer
     };
 
+    enum DropProtection {
+        DropProtectionSync,
+        DropProtectionAsync,
+    };
+
     virtual void contextDestroyed();
     virtual void didTimeout();
     virtual bool canSuspend() const;
@@ -176,7 +181,7 @@ private:
     void callReadyStateChangeListener();
     void dropProtectionSoon();
     void dropProtection(Timer<XMLHttpRequest>* = 0);
-    void internalAbort();
+    void internalAbort(DropProtection);
     void clearResponse();
     void clearResponseBuffers();
     void clearRequest();