Replace Maybe with std::optional

With c++17, std::optional provides the functionality that Maybe
provided.

Bug: 183215655
Test: aapt2_tests
Change-Id: I62bb9c2fa4985dc5217a6ed153df92b85ad9a034
diff --git a/tools/aapt2/configuration/ConfigurationParser_test.cpp b/tools/aapt2/configuration/ConfigurationParser_test.cpp
index e5b3107..e5eaccc 100644
--- a/tools/aapt2/configuration/ConfigurationParser_test.cpp
+++ b/tools/aapt2/configuration/ConfigurationParser_test.cpp
@@ -31,11 +31,6 @@
 namespace aapt {
 
 namespace configuration {
-void PrintTo(const AndroidSdk& sdk, std::ostream* os) {
-  *os << "SDK: min=" << sdk.min_sdk_version
-      << ", target=" << sdk.target_sdk_version.value_or_default(-1)
-      << ", max=" << sdk.max_sdk_version.value_or_default(-1);
-}
 
 bool operator==(const ConfiguredArtifact& lhs, const ConfiguredArtifact& rhs) {
   return lhs.name == rhs.name && lhs.abi_group == rhs.abi_group &&
@@ -45,20 +40,6 @@
          lhs.gl_texture_group == rhs.gl_texture_group;
 }
 
-std::ostream& operator<<(std::ostream& out, const Maybe<std::string>& value) {
-  PrintTo(value, &out);
-  return out;
-}
-
-void PrintTo(const ConfiguredArtifact& artifact, std::ostream* os) {
-  *os << "\n{"
-      << "\n  name: " << artifact.name << "\n  sdk: " << artifact.android_sdk
-      << "\n  abi: " << artifact.abi_group << "\n  density: " << artifact.screen_density_group
-      << "\n  locale: " << artifact.locale_group
-      << "\n  features: " << artifact.device_feature_group
-      << "\n  textures: " << artifact.gl_texture_group << "\n}\n";
-}
-
 namespace handler {
 
 namespace {
@@ -186,7 +167,7 @@
 }
 
 TEST_F(ConfigurationParserTest, ExtractConfiguration) {
-  Maybe<PostProcessingConfiguration> maybe_config =
+  std::optional<PostProcessingConfiguration> maybe_config =
       ExtractConfiguration(kValidConfig, "fake.xml", &diag_);
 
   PostProcessingConfiguration config = maybe_config.value();
@@ -928,7 +909,8 @@
 
   EXPECT_FALSE(x86.ToArtifactName("something.${abi${density}}.apk", "", &diag));
 
-  const Maybe<std::string>& name = x86.ToArtifactName("something.${abi${abi}}.apk", "", &diag);
+  const std::optional<std::string>& name =
+      x86.ToArtifactName("something.${abi${abi}}.apk", "", &diag);
   ASSERT_TRUE(name);
   EXPECT_EQ(name.value(), "something.${abix86}.apk");
 }