Replace rtc::Optional with absl::optional in rtc_base

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

This CL generated by running script with parameter 'rtc_base'
Then manually fix where Optional was used without rtc prefix (patchset#3)

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: I825f80cc8089747876ba6316d9e7c30e05716974
Reviewed-on: https://webrtc-review.googlesource.com/84585
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23700}
diff --git a/rtc_base/string_to_number_unittest.cc b/rtc_base/string_to_number_unittest.cc
index 691b26f..f7bf484 100644
--- a/rtc_base/string_to_number_unittest.cc
+++ b/rtc_base/string_to_number_unittest.cc
@@ -68,10 +68,10 @@
       (min_value == 0) ? "-2" : (std::to_string(min_value) + "1");
   // Make the large value approximately ten times larger than the maximum.
   const std::string too_large_string = std::to_string(max_value) + "1";
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(too_low_string));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(too_low_string.c_str()));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(too_large_string));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(too_large_string.c_str()));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(too_low_string));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(too_low_string.c_str()));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(too_large_string));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(too_large_string.c_str()));
 }
 
 TYPED_TEST_P(BasicNumberTest, TestInvalidInputs) {
@@ -79,18 +79,18 @@
   const char kInvalidCharArray[] = "Invalid string containing 47";
   const char kPlusMinusCharArray[] = "+-100";
   const char kNumberFollowedByCruft[] = "640x480";
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(kInvalidCharArray));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(std::string(kInvalidCharArray)));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(kPlusMinusCharArray));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(std::string(kPlusMinusCharArray)));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(kNumberFollowedByCruft));
-  EXPECT_EQ(rtc::nullopt,
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(kInvalidCharArray));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(std::string(kInvalidCharArray)));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(kPlusMinusCharArray));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(std::string(kPlusMinusCharArray)));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(kNumberFollowedByCruft));
+  EXPECT_EQ(absl::nullopt,
             StringToNumber<T>(std::string(kNumberFollowedByCruft)));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(" 5"));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(" - 5"));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>("- 5"));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>(" -5"));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<T>("5 "));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(" 5"));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(" - 5"));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>("- 5"));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>(" -5"));
+  EXPECT_EQ(absl::nullopt, StringToNumber<T>("5 "));
 }
 
 REGISTER_TYPED_TEST_CASE_P(BasicNumberTest,
@@ -105,10 +105,10 @@
                               IntegerTypes);
 
 TEST(StringToNumberTest, TestSpecificValues) {
-  EXPECT_EQ(rtc::nullopt, StringToNumber<uint8_t>("256"));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<uint8_t>("-256"));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<int8_t>("256"));
-  EXPECT_EQ(rtc::nullopt, StringToNumber<int8_t>("-256"));
+  EXPECT_EQ(absl::nullopt, StringToNumber<uint8_t>("256"));
+  EXPECT_EQ(absl::nullopt, StringToNumber<uint8_t>("-256"));
+  EXPECT_EQ(absl::nullopt, StringToNumber<int8_t>("256"));
+  EXPECT_EQ(absl::nullopt, StringToNumber<int8_t>("-256"));
 }
 
 }  // namespace rtc