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.h b/webrtc/test/testsupport/fileutils.h
index 570d7b4..5ea7d31 100644
--- a/webrtc/test/testsupport/fileutils.h
+++ b/webrtc/test/testsupport/fileutils.h
@@ -16,7 +16,7 @@
#include <string>
#include <vector>
-#include "webrtc/rtc_base/optional.h"
+#include "webrtc/api/optional.h"
namespace webrtc {
namespace test {