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/api/mediastreaminterface.h b/webrtc/api/mediastreaminterface.h
index aaf5b62..5d65447 100644
--- a/webrtc/api/mediastreaminterface.h
+++ b/webrtc/api/mediastreaminterface.h
@@ -22,8 +22,8 @@
#include <string>
#include <vector>
+#include "webrtc/api/optional.h"
#include "webrtc/api/video/video_frame.h"
-#include "webrtc/rtc_base/optional.h"
// TODO(zhihuang): Remove unrelated headers once downstream applications stop
// relying on them; they were previously transitively included by
// mediachannel.h, which is no longer a dependency of this file.