Pass ProgramStateRef by reference.

Retain + Release on a ref counted pointer is cheap, but not free (it adds a function call in this case).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@157534 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h b/include/clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h
index 46fbb88..40969d3 100644
--- a/include/clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h
+++ b/include/clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h
@@ -151,7 +151,7 @@
 
   static void Profile(llvm::FoldingSetNodeID &ID,
                       const ProgramPoint &Loc,
-                      ProgramStateRef state,
+                      const ProgramStateRef &state,
                       bool IsSink) {
     ID.Add(Loc);
     ID.AddPointer(state.getPtr());