Remove unnecessary .c_str() when implicitly converting to Twine

llvm-svn: 221422
diff --git a/llvm/lib/Support/SourceMgr.cpp b/llvm/lib/Support/SourceMgr.cpp
index f3a422c..b50a66b2 100644
--- a/llvm/lib/Support/SourceMgr.cpp
+++ b/llvm/lib/Support/SourceMgr.cpp
@@ -49,14 +49,14 @@
                                    std::string &IncludedFile) {
   IncludedFile = Filename;
   ErrorOr<std::unique_ptr<MemoryBuffer>> NewBufOrErr =
-      MemoryBuffer::getFile(IncludedFile.c_str());
+    MemoryBuffer::getFile(IncludedFile);
 
   // If the file didn't exist directly, see if it's in an include path.
   for (unsigned i = 0, e = IncludeDirectories.size(); i != e && !NewBufOrErr;
        ++i) {
     IncludedFile =
         IncludeDirectories[i] + sys::path::get_separator().data() + Filename;
-    NewBufOrErr = MemoryBuffer::getFile(IncludedFile.c_str());
+    NewBufOrErr = MemoryBuffer::getFile(IncludedFile);
   }
 
   if (!NewBufOrErr)