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/modules/video_coding/utility/quality_scaler.h b/webrtc/modules/video_coding/utility/quality_scaler.h
index 690d1bc..25d39cc 100644
--- a/webrtc/modules/video_coding/utility/quality_scaler.h
+++ b/webrtc/modules/video_coding/utility/quality_scaler.h
@@ -13,10 +13,10 @@
#include <utility>
+#include "webrtc/api/optional.h"
#include "webrtc/api/video_codecs/video_encoder.h"
#include "webrtc/common_types.h"
#include "webrtc/modules/video_coding/utility/moving_average.h"
-#include "webrtc/rtc_base/optional.h"
#include "webrtc/rtc_base/sequenced_task_checker.h"
namespace webrtc {