Return a std::unique_ptr from getBufferForFile. NFC.

llvm-svn: 216476
diff --git a/clang/lib/Basic/SourceManager.cpp b/clang/lib/Basic/SourceManager.cpp
index 14de760..ef52e82 100644
--- a/clang/lib/Basic/SourceManager.cpp
+++ b/clang/lib/Basic/SourceManager.cpp
@@ -96,9 +96,9 @@
 
   std::string ErrorStr;
   bool isVolatile = SM.userFilesAreVolatile() && !IsSystemFile;
-  Buffer.setPointer(SM.getFileManager().getBufferForFile(ContentsEntry,
-                                                         &ErrorStr,
-                                                         isVolatile));
+  Buffer.setPointer(SM.getFileManager()
+                        .getBufferForFile(ContentsEntry, &ErrorStr, isVolatile)
+                        .release());
 
   // If we were unable to open the file, then we are in an inconsistent
   // situation where the content cache referenced a file which no longer