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/MC/MCExpr.cpp b/lib/MC/MCExpr.cpp
index c950ff2..a5a2256 100644
--- a/lib/MC/MCExpr.cpp
+++ b/lib/MC/MCExpr.cpp
@@ -133,8 +133,7 @@
   return new (Ctx) MCSymbolRefExpr(Sym);
 }
 
-const MCSymbolRefExpr *MCSymbolRefExpr::Create(const StringRef &Name,
-                                               MCContext &Ctx) {
+const MCSymbolRefExpr *MCSymbolRefExpr::Create(StringRef Name, MCContext &Ctx) {
   return Create(Ctx.GetOrCreateSymbol(Name), Ctx);
 }