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 d7a37156d1dafb15073e8d37113514285b486755..3e15efb783dad7fbf4aca5eddb6732239a707f9c 100644
--- a/Source/core/xml/XMLHttpRequest.h
+++ b/Source/core/xml/XMLHttpRequest.h
@@ -75,6 +75,11 @@ public:
         ResponseTypeArrayBuffer
     };
 
+    enum DropProtection {
+        DropProtectionSync,
+        DropProtectionAsync,
+    };
+
     virtual void contextDestroyed();
     virtual void didTimeout();
     virtual bool canSuspend() const;
@@ -169,7 +174,7 @@ private:
     void callReadyStateChangeListener();
     void dropProtectionSoon();
     void dropProtection(Timer<XMLHttpRequest>* = 0);
-    void internalAbort();
+    void internalAbort(DropProtection = DropProtectionSync);
     void clearResponse();
     void clearResponseBuffers();
     void clearRequest();