Bug 587944. Save and restore the target frame when we dispatch a synth mouse enter/exit event.

content/events/src/nsEventStateManager.cpp

@@ -3294,6 +3294,7 @@ nsEventStateManager::PostHandleEvent(nsPresContext* aPresContext,
 
   //Reset target frame to null to avoid mistargeting after reentrant event
   mCurrentTarget = nsnull;
+  mCurrentTargetContent = nsnull;
 
   return ret;
 }
@@ -3612,6 +3613,8 @@ nsEventStateManager::DispatchMouseEvent(nsGUIEvent* aEvent, PRUint32 aMessage,
   event.relatedTarget = aRelatedContent;
   event.inputSource = static_cast<nsMouseEvent*>(aEvent)->inputSource;
 
+  nsWeakFrame previousTarget = mCurrentTarget;
+
   mCurrentTargetContent = aTargetContent;
 
   nsIFrame* targetFrame = nsnull;
@@ -3629,6 +3632,7 @@ nsEventStateManager::DispatchMouseEvent(nsGUIEvent* aEvent, PRUint32 aMessage,
   }
 
   mCurrentTargetContent = nsnull;
+  mCurrentTarget = previousTarget;
 
   return targetFrame;
 }