Add explicit keywords.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47382 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index d1de88b..244dee3 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -262,7 +262,7 @@
   public SelectionDAG::DAGUpdateListener {
   DAGCombiner &DC;
 public:
-  WorkListRemover(DAGCombiner &dc) : DC(dc) {}
+  explicit WorkListRemover(DAGCombiner &dc) : DC(dc) {}
   
   virtual void NodeDeleted(SDNode *N) {
     DC.removeFromWorkList(N);