Fix MemoryBuffer breakage correctly.

llvm-svn: 36561
diff --git a/llvm/lib/Support/MemoryBuffer.cpp b/llvm/lib/Support/MemoryBuffer.cpp
index 3c1ee90..9603535 100644
--- a/llvm/lib/Support/MemoryBuffer.cpp
+++ b/llvm/lib/Support/MemoryBuffer.cpp
@@ -159,7 +159,7 @@
 
 MemoryBuffer *MemoryBuffer::getFile(const char *FilenameStart, unsigned FnSize,
                                     int64_t FileSize) {
-  sys::PathWithStatus P(std::string(FilenameStart, FnSize));
+  sys::PathWithStatus P(FilenameStart, FnSize);
 #if 1
   return new MemoryBufferMMapFile(P);
 #else