Optional: Use nullopt and implicit construction in /rtc_base

Changes places where we explicitly construct an Optional to instead use
nullopt or the requisite value type only.

This CL was uploaded by git cl split.

Bug: None
Change-Id: I2c1e50090e48c892fda74f1678231a7624cac9fa
Reviewed-on: https://webrtc-review.googlesource.com/23575
Commit-Queue: Oskar Sundbom <ossu@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20884}
diff --git a/rtc_base/string_to_number_unittest.cc b/rtc_base/string_to_number_unittest.cc
index 5a6a237..f5e5b573 100644
--- a/rtc_base/string_to_number_unittest.cc
+++ b/rtc_base/string_to_number_unittest.cc
@@ -67,10 +67,10 @@
       (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::Optional<T>(), StringToNumber<T>(too_low_string));
-  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(too_low_string.c_str()));
-  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(too_large_string));
-  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(too_large_string.c_str()));
+  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()));
 }
 
 TYPED_TEST_P(BasicNumberTest, TestInvalidInputs) {
@@ -78,20 +78,18 @@
   const char kInvalidCharArray[] = "Invalid string containing 47";
   const char kPlusMinusCharArray[] = "+-100";
   const char kNumberFollowedByCruft[] = "640x480";
-  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(kInvalidCharArray));
-  EXPECT_EQ(rtc::Optional<T>(),
-            StringToNumber<T>(std::string(kInvalidCharArray)));
-  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(kPlusMinusCharArray));
-  EXPECT_EQ(rtc::Optional<T>(),
-            StringToNumber<T>(std::string(kPlusMinusCharArray)));
-  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(kNumberFollowedByCruft));
-  EXPECT_EQ(rtc::Optional<T>(),
+  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,
             StringToNumber<T>(std::string(kNumberFollowedByCruft)));
-  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(" 5"));
-  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(" - 5"));
-  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>("- 5"));
-  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(" -5"));
-  EXPECT_EQ(rtc::Optional<T>(), 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(rtc::nullopt, StringToNumber<T>("5 "));
 }
 
 REGISTER_TYPED_TEST_CASE_P(BasicNumberTest,
@@ -106,10 +104,10 @@
                               IntegerTypes);
 
 TEST(StringToNumberTest, TestSpecificValues) {
-  EXPECT_EQ(rtc::Optional<uint8_t>(), StringToNumber<uint8_t>("256"));
-  EXPECT_EQ(rtc::Optional<uint8_t>(), StringToNumber<uint8_t>("-256"));
-  EXPECT_EQ(rtc::Optional<int8_t>(), StringToNumber<int8_t>("256"));
-  EXPECT_EQ(rtc::Optional<int8_t>(), StringToNumber<int8_t>("-256"));
+  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"));
 }
 
 }  // namespace rtc