Move optional.h to webrtc/api/

webrtc/modules/audio_processing/aec3/block_processor.cc

Index: webrtc/modules/audio_processing/aec3/block_processor.cc
diff --git a/webrtc/modules/audio_processing/aec3/block_processor.cc b/webrtc/modules/audio_processing/aec3/block_processor.cc
index 536335e8a26bdd420773c0d00fc3662df91dbc38..7bb9e15129af389f38fa2e6de3c5205191583801 100644
--- a/webrtc/modules/audio_processing/aec3/block_processor.cc
+++ b/webrtc/modules/audio_processing/aec3/block_processor.cc
@@ -9,13 +9,13 @@
  */
 #include "webrtc/modules/audio_processing/aec3/block_processor.h"
 
+#include "webrtc/api/optional.h"
 #include "webrtc/modules/audio_processing/aec3/aec3_common.h"
 #include "webrtc/modules/audio_processing/aec3/block_processor_metrics.h"
 #include "webrtc/modules/audio_processing/aec3/echo_path_variability.h"
 #include "webrtc/modules/audio_processing/logging/apm_data_dumper.h"
 #include "webrtc/rtc_base/atomicops.h"
 #include "webrtc/rtc_base/constructormagic.h"
-#include "webrtc/rtc_base/optional.h"
 
 namespace webrtc {
 namespace {