fix crash by removing DisplayZTreeNode's from the mMapPlaceholderViewToZTreeNode hashtable in DestroyZTreeNode. bug 78661. r=roc+moz sr=attinasi

view/src/nsViewManager.cpp

@@ -168,8 +168,14 @@ struct DisplayZTreeNode {
   DisplayListElement2* mDisplayElement;  // tree leaf nodes
 };
 
-static void DestroyZTreeNode(DisplayZTreeNode* aNode) {
-  if (nsnull != aNode) {
+void nsViewManager::DestroyZTreeNode(DisplayZTreeNode* aNode) 
+{
+  if (aNode) {
+    if (mMapPlaceholderViewToZTreeNode.Count() > 0) {
+       nsVoidKey key(aNode->mView);
+       DisplayZTreeNode* placeholder = (DisplayZTreeNode *)mMapPlaceholderViewToZTreeNode.Remove(&key);
+    }
+  
     DestroyZTreeNode(aNode->mZChild);
     DestroyZTreeNode(aNode->mZSibling);
     delete aNode->mDisplayElement;

view/src/nsViewManager.h

@@ -382,7 +382,7 @@ private:
   nsIRenderingContext *mWhiteCX;
 
   nsISupportsArray  *mCompositeListeners;
- 
+  void DestroyZTreeNode(DisplayZTreeNode* aNode);
 protected:
   nsIView           *mRootView;
   nscoord           mX;