[analyzer] Rename trackNullOrUndefValue to trackExpressionValue

trackNullOrUndefValue is a long and confusing name,
and it does not actually reflect what the function is doing.
Give a function a new name, with a relatively clear semantics.

Also remove some dead code.

Differential Revision: https://reviews.llvm.org/D52758

llvm-svn: 345064
diff --git a/clang/lib/StaticAnalyzer/Checkers/NonNullParamChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/NonNullParamChecker.cpp
index 01d2c04..a97eab4 100644
--- a/clang/lib/StaticAnalyzer/Checkers/NonNullParamChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/NonNullParamChecker.cpp
@@ -192,7 +192,7 @@
       *BTAttrNonNull,
       "Null pointer passed as an argument to a 'nonnull' parameter", ErrorNode);
   if (ArgE)
-    bugreporter::trackNullOrUndefValue(ErrorNode, ArgE, *R);
+    bugreporter::trackExpressionValue(ErrorNode, ArgE, *R);
 
   return R;
 }
@@ -208,9 +208,7 @@
     const Expr *ArgEDeref = bugreporter::getDerefExpr(ArgE);
     if (!ArgEDeref)
       ArgEDeref = ArgE;
-    bugreporter::trackNullOrUndefValue(ErrorNode,
-                                       ArgEDeref,
-                                       *R);
+    bugreporter::trackExpressionValue(ErrorNode, ArgEDeref, *R);
   }
   return R;