Move optional.h to webrtc/api/
We use Optional in our public API, so its header should be in
webrtc/api/.
BUG=webrtc:8205
Review-Url: https://codereview.webrtc.org/3011943002
Cr-Commit-Position: refs/heads/master@{#19693}
diff --git a/webrtc/test/testsupport/fileutils_unittest.cc b/webrtc/test/testsupport/fileutils_unittest.cc
index bdabb84..fb780be 100644
--- a/webrtc/test/testsupport/fileutils_unittest.cc
+++ b/webrtc/test/testsupport/fileutils_unittest.cc
@@ -17,8 +17,8 @@
#include <list>
#include <string>
+#include "webrtc/api/optional.h"
#include "webrtc/rtc_base/checks.h"
-#include "webrtc/rtc_base/optional.h"
#include "webrtc/rtc_base/pathutils.h"
#include "webrtc/test/gtest.h"