Use StringRef in StringSaver API (NFC)

llvm-svn: 283290
diff --git a/llvm/lib/Support/StringSaver.cpp b/llvm/lib/Support/StringSaver.cpp
index bbc1fd2..335fce3 100644
--- a/llvm/lib/Support/StringSaver.cpp
+++ b/llvm/lib/Support/StringSaver.cpp
@@ -11,9 +11,9 @@
 
 using namespace llvm;
 
-const char *StringSaver::save(StringRef S) {
+StringRef StringSaver::save(StringRef S) {
   char *P = Alloc.Allocate<char>(S.size() + 1);
   memcpy(P, S.data(), S.size());
   P[S.size()] = '\0';
-  return P;
+  return StringRef(P, S.size());
 }