[analyzer] Rename addTrackNullOrUndefValueVisitor to trackNullOrUndefValue.

This helper function (in the clang::ento::bugreporter namespace) may add more
than one visitor, but conceptually it's tracking a single use of a null or
undefined value and should do so as best it can.

Also, the BugReport parameter has been made a reference to underscore that
it is non-optional.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@162720 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp b/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp
index e98c131..cb0a3ce 100644
--- a/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp
@@ -166,8 +166,7 @@
                   buf.empty() ? BT_null->getDescription() : buf.str(),
                   N);
 
-  bugreporter::addTrackNullOrUndefValueVisitor(N, bugreporter::GetDerefExpr(N),
-                                               report);
+  bugreporter::trackNullOrUndefValue(N, bugreporter::GetDerefExpr(N), *report);
 
   for (SmallVectorImpl<SourceRange>::iterator
        I = Ranges.begin(), E = Ranges.end(); I!=E; ++I)
@@ -191,9 +190,8 @@
 
       BugReport *report =
         new BugReport(*BT_undef, BT_undef->getDescription(), N);
-      bugreporter::addTrackNullOrUndefValueVisitor(N,
-                                                   bugreporter::GetDerefExpr(N),
-                                                   report);
+      bugreporter::trackNullOrUndefValue(N, bugreporter::GetDerefExpr(N),
+                                         *report);
       report->disablePathPruning();
       C.EmitReport(report);
     }