Bug 1156108 - Make nsTreeColumns::mFirstColumn an nsRefPtr; r=roc

layout/xul/tree/nsTreeColumns.cpp

@@ -393,8 +393,7 @@ nsTreeColumn::Invalidate(mozilla::ErrorResult& aRv)
 }
 
 nsTreeColumns::nsTreeColumns(nsTreeBodyFrame* aTree)
-  : mTree(aTree),
-    mFirstColumn(nullptr)
+  : mTree(aTree)
 {
 }
 
@@ -669,7 +668,7 @@ nsTreeColumns::InvalidateColumns()
        currCol = currCol->GetNext()) {
     currCol->SetColumns(nullptr);
   }
-  NS_IF_RELEASE(mFirstColumn);
+  mFirstColumn = nullptr;
   return NS_OK;
 }
 
@@ -759,7 +758,7 @@ nsTreeColumns::EnsureColumns()
           col->SetPrevious(currCol);
         }
         else {
-          NS_ADDREF(mFirstColumn = col);
+          mFirstColumn = col;
         }
         currCol = col;
       }

layout/xul/tree/nsTreeColumns.h

@@ -211,7 +211,7 @@ private:
    * XXX this means that new nsTreeColumn objects are unnecessarily created
    *     for untouched columns.
    */
-  nsTreeColumn* mFirstColumn;
+  nsRefPtr<nsTreeColumn> mFirstColumn;
 };
 
 #endif // nsTreeColumns_h__