Use StringRef instead of std::string.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140154 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Instrumentation/GCOVProfiling.cpp b/lib/Transforms/Instrumentation/GCOVProfiling.cpp
index e701f99..d55f0fa 100644
--- a/lib/Transforms/Instrumentation/GCOVProfiling.cpp
+++ b/lib/Transforms/Instrumentation/GCOVProfiling.cpp
@@ -186,7 +186,7 @@
   // other blocks.
   class GCOVBlock : public GCOVRecord {
    public:
-    GCOVLines &getFile(std::string Filename) {
+    GCOVLines &getFile(StringRef Filename) {
       GCOVLines *&Lines = LinesByFile[Filename];
       if (!Lines) {
         Lines = new GCOVLines(os);