BIND 10 trac2750, updated. 7b722a23d6a85ad0c3d903323e9a36ea2baefa0a [2750] Add a comment about why down_ is not swapped

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- Log -----------------------------------------------------------------
commit 7b722a23d6a85ad0c3d903323e9a36ea2baefa0a
Author: Mukund Sivaraman <muks at isc.org>
Date:   Mon Aug 26 15:06:27 2013 +0530

    [2750] Add a comment about why down_ is not swapped

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Summary of changes:
 src/lib/datasrc/memory/domaintree.h |    3 +++
 1 file changed, 3 insertions(+)

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diff --git a/src/lib/datasrc/memory/domaintree.h b/src/lib/datasrc/memory/domaintree.h
index ace435f..b2f402d 100644
--- a/src/lib/datasrc/memory/domaintree.h
+++ b/src/lib/datasrc/memory/domaintree.h
@@ -632,6 +632,9 @@ private:
     ///
     /// This method doesn't throw any exceptions.
     void exchange(DomainTreeNode<T>* other, DomainTreeNodePtr* subtree_root) {
+        // Swap the pointers first. down should not be swapped as it
+        // belongs to the node's data, and not to its position in the
+        // tree.
         std::swap(left_, other->left_);
         if (other->getLeft() == other) {
             other->left_ = this;