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/xml/XmlDom_test.cpp b/tools/aapt2/xml/XmlDom_test.cpp
index ca46d53..6c717dc 100644
--- a/tools/aapt2/xml/XmlDom_test.cpp
+++ b/tools/aapt2/xml/XmlDom_test.cpp
@@ -98,7 +98,7 @@
   // the Attribute accepts (eg: string|reference).
   ASSERT_TRUE(new_doc->root->attributes[0].compiled_attribute);
   EXPECT_THAT(new_doc->root->attributes[0].compiled_attribute.value().id,
-              Eq(make_value(ResourceId(0x01010001u))));
+              Eq(ResourceId(0x01010001u)));
 
   EXPECT_THAT(new_doc->root->attributes[0].value, StrEq("@string/foo"));
   EXPECT_THAT(new_doc->root->attributes[0].compiled_value,
@@ -145,21 +145,19 @@
 
   void Visit(Element* el) override {
     if (el->name == "View1") {
-      EXPECT_THAT(TransformPackageAlias("one"), Eq(make_value(ExtractedPackage{"com.one", false})));
+      EXPECT_THAT(TransformPackageAlias("one"), Eq(ExtractedPackage{"com.one", false}));
     } else if (el->name == "View2") {
-      EXPECT_THAT(TransformPackageAlias("one"), Eq(make_value(ExtractedPackage{"com.one", false})));
-      EXPECT_THAT(TransformPackageAlias("two"), Eq(make_value(ExtractedPackage{"com.two", false})));
+      EXPECT_THAT(TransformPackageAlias("one"), Eq(ExtractedPackage{"com.one", false}));
+      EXPECT_THAT(TransformPackageAlias("two"), Eq(ExtractedPackage{"com.two", false}));
     } else if (el->name == "View3") {
-      EXPECT_THAT(TransformPackageAlias("one"), Eq(make_value(ExtractedPackage{"com.one", false})));
-      EXPECT_THAT(TransformPackageAlias("two"), Eq(make_value(ExtractedPackage{"com.two", false})));
-      EXPECT_THAT(TransformPackageAlias("three"),
-                  Eq(make_value(ExtractedPackage{"com.three", false})));
+      EXPECT_THAT(TransformPackageAlias("one"), Eq(ExtractedPackage{"com.one", false}));
+      EXPECT_THAT(TransformPackageAlias("two"), Eq(ExtractedPackage{"com.two", false}));
+      EXPECT_THAT(TransformPackageAlias("three"), Eq(ExtractedPackage{"com.three", false}));
     } else if (el->name == "View4") {
-      EXPECT_THAT(TransformPackageAlias("one"), Eq(make_value(ExtractedPackage{"com.one", false})));
-      EXPECT_THAT(TransformPackageAlias("two"), Eq(make_value(ExtractedPackage{"com.two", false})));
-      EXPECT_THAT(TransformPackageAlias("three"),
-                  Eq(make_value(ExtractedPackage{"com.three", false})));
-      EXPECT_THAT(TransformPackageAlias("four"), Eq(make_value(ExtractedPackage{"", true})));
+      EXPECT_THAT(TransformPackageAlias("one"), Eq(ExtractedPackage{"com.one", false}));
+      EXPECT_THAT(TransformPackageAlias("two"), Eq(ExtractedPackage{"com.two", false}));
+      EXPECT_THAT(TransformPackageAlias("three"), Eq(ExtractedPackage{"com.three", false}));
+      EXPECT_THAT(TransformPackageAlias("four"), Eq(ExtractedPackage{"", true}));
     }
   }
 };