Replace rtc::Optional with absl::optional

This is a no-op change because rtc::Optional is an alias to absl::optional

This CL generated by running script from modules with parameters
'pacing video_coding congestion_controller remote_bitrate_estimator':

find $@ -type f \( -name \*.h -o -name \*.cc \) \
-exec sed -i 's|rtc::Optional|absl::optional|g' {} \+ \
-exec sed -i 's|rtc::nullopt|absl::nullopt|g' {} \+ \
-exec sed -i 's|#include "api/optional.h"|#include "absl/types/optional.h"|' {} \+

find $@ -type f -name BUILD.gn \
-exec sed -r -i 's|"(../)*api:optional"|"//third_party/abseil-cpp/absl/types:optional"|' {} \+;

git cl format

Bug: webrtc:9078
Change-Id: I8ea501d7f1ee36e8d8cd3ed37e6b763c7fe29118
Reviewed-on: https://webrtc-review.googlesource.com/83900
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23640}
diff --git a/modules/video_coding/generic_encoder.cc b/modules/video_coding/generic_encoder.cc
index 69357ee..202cc86 100644
--- a/modules/video_coding/generic_encoder.cc
+++ b/modules/video_coding/generic_encoder.cc
@@ -12,7 +12,7 @@
 
 #include <vector>
 
-#include "api/optional.h"
+#include "absl/types/optional.h"
 #include "api/video/i420_buffer.h"
 #include "modules/include/module_common_types_public.h"
 #include "modules/video_coding/encoded_frame.h"
@@ -178,7 +178,7 @@
       incorrect_capture_time_logged_messages_(0),
       reordered_frames_logged_messages_(0),
       stalled_encoder_logged_messages_(0) {
-  rtc::Optional<AlrExperimentSettings> experiment_settings =
+  absl::optional<AlrExperimentSettings> experiment_settings =
       AlrExperimentSettings::CreateFromFieldTrial(
           AlrExperimentSettings::kStrictPacingAndProbingExperimentName);
   if (experiment_settings) {
@@ -249,10 +249,10 @@
       rtp_timestamp, capture_time_ms, rtc::TimeMillis());
 }
 
-rtc::Optional<int64_t> VCMEncodedFrameCallback::ExtractEncodeStartTime(
+absl::optional<int64_t> VCMEncodedFrameCallback::ExtractEncodeStartTime(
     size_t simulcast_svc_idx,
     EncodedImage* encoded_image) {
-  rtc::Optional<int64_t> result;
+  absl::optional<int64_t> result;
   size_t num_simulcast_svc_streams = timing_frames_info_.size();
   if (simulcast_svc_idx < num_simulcast_svc_streams) {
     auto encode_start_list =
@@ -308,8 +308,8 @@
 
 void VCMEncodedFrameCallback::FillTimingInfo(size_t simulcast_svc_idx,
                                              EncodedImage* encoded_image) {
-  rtc::Optional<size_t> outlier_frame_size;
-  rtc::Optional<int64_t> encode_start_ms;
+  absl::optional<size_t> outlier_frame_size;
+  absl::optional<int64_t> encode_start_ms;
   uint8_t timing_flags = VideoSendTiming::kNotTriggered;
   {
     rtc::CritScope crit(&timing_params_lock_);