Convert a few ownership comments with std::unique_ptr.

llvm-svn: 215853
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 070b00c..fbfad94 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -2034,7 +2034,7 @@
     }
 
     IntrusiveRefCntPtr<vfs::FileSystem> FS =
-        vfs::getVFSFromYAML(Buffer->release(), /*DiagHandler*/ nullptr);
+        vfs::getVFSFromYAML(std::move(Buffer.get()), /*DiagHandler*/ nullptr);
     if (!FS.get()) {
       Diags.Report(diag::err_invalid_vfs_overlay) << File;
       return IntrusiveRefCntPtr<vfs::FileSystem>();