Pass StringRef by value.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86251 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/StringRef.cpp b/lib/Support/StringRef.cpp
index deaa19e..3f3ee5b 100644
--- a/lib/Support/StringRef.cpp
+++ b/lib/Support/StringRef.cpp
@@ -24,7 +24,7 @@
 ///
 /// \return - The index of the first occurence of \arg Str, or npos if not
 /// found.
-size_t StringRef::find(const StringRef &Str) const {
+size_t StringRef::find(StringRef Str) const {
   size_t N = Str.size();
   if (N > Length)
     return npos;
@@ -38,7 +38,7 @@
 ///
 /// \return - The index of the last occurence of \arg Str, or npos if not
 /// found.
-size_t StringRef::rfind(const StringRef &Str) const {
+size_t StringRef::rfind(StringRef Str) const {
   size_t N = Str.size();
   if (N > Length)
     return npos;
@@ -75,7 +75,7 @@
 
 /// count - Return the number of non-overlapped occurrences of \arg Str in
 /// the string.
-size_t StringRef::count(const StringRef &Str) const {
+size_t StringRef::count(StringRef Str) const {
   size_t Count = 0;
   size_t N = Str.size();
   if (N > Length)