yaml::Stream doesn't need to take ownership of the buffer.

In fact, most users were already using the StringRef version.

llvm-svn: 216575
diff --git a/llvm/unittests/Support/YAMLParserTest.cpp b/llvm/unittests/Support/YAMLParserTest.cpp
index 1a5188a..6374638 100644
--- a/llvm/unittests/Support/YAMLParserTest.cpp
+++ b/llvm/unittests/Support/YAMLParserTest.cpp
@@ -212,7 +212,7 @@
   // we get its ID as filename in diagnostics.
   std::unique_ptr<MemoryBuffer> Buffer(
       MemoryBuffer::getMemBuffer("[]", "buffername.yaml"));
-  yaml::Stream Stream(std::move(Buffer), SM);
+  yaml::Stream Stream(Buffer->getMemBufferRef(), SM);
   Stream.printError(Stream.begin()->getRoot(), "Hello, World!");
   EXPECT_EQ("buffername.yaml", GeneratedDiag.getFilename());
 }