Replace rtc::Optional with absl::optional in test and rtc_tools

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

This CL generated by running script with parameters 'test rtc_tools'

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: Ibb43c737f4c45fe300736382b0dd2d8ab32c6377
Reviewed-on: https://webrtc-review.googlesource.com/83944
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23642}
diff --git a/test/mock_audio_decoder_factory.h b/test/mock_audio_decoder_factory.h
index 3a43997..247f9fa 100644
--- a/test/mock_audio_decoder_factory.h
+++ b/test/mock_audio_decoder_factory.h
@@ -28,14 +28,14 @@
   MOCK_METHOD1(IsSupportedDecoder, bool(const SdpAudioFormat&));
   std::unique_ptr<AudioDecoder> MakeAudioDecoder(
       const SdpAudioFormat& format,
-      rtc::Optional<AudioCodecPairId> codec_pair_id) {
+      absl::optional<AudioCodecPairId> codec_pair_id) {
     std::unique_ptr<AudioDecoder> return_value;
     MakeAudioDecoderMock(format, codec_pair_id, &return_value);
     return return_value;
   }
   MOCK_METHOD3(MakeAudioDecoderMock,
                void(const SdpAudioFormat& format,
-                    rtc::Optional<AudioCodecPairId> codec_pair_id,
+                    absl::optional<AudioCodecPairId> codec_pair_id,
                     std::unique_ptr<AudioDecoder>* return_value));
 
   // Creates a MockAudioDecoderFactory with no formats and that may not be