keep only the StringRef version of getFileOrSTDIN.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184826 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AsmParser/Parser.cpp b/lib/AsmParser/Parser.cpp
index bb4f03b..d777ab9 100644
--- a/lib/AsmParser/Parser.cpp
+++ b/lib/AsmParser/Parser.cpp
@@ -43,7 +43,7 @@
 Module *llvm::ParseAssemblyFile(const std::string &Filename, SMDiagnostic &Err,
                                 LLVMContext &Context) {
   OwningPtr<MemoryBuffer> File;
-  if (error_code ec = MemoryBuffer::getFileOrSTDIN(Filename.c_str(), File)) {
+  if (error_code ec = MemoryBuffer::getFileOrSTDIN(Filename, File)) {
     Err = SMDiagnostic(Filename, SourceMgr::DK_Error,
                        "Could not open input file: " + ec.message());
     return 0;