raw_ostream: Forward declare OpenFlags and include FileSystem.h only where necessary.

llvm-svn: 207593
diff --git a/llvm/unittests/LineEditor/LineEditor.cpp b/llvm/unittests/LineEditor/LineEditor.cpp
index cb115bd..26053c0 100644
--- a/llvm/unittests/LineEditor/LineEditor.cpp
+++ b/llvm/unittests/LineEditor/LineEditor.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/LineEditor/LineEditor.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 #include "gtest/gtest.h"