headless: Replace headless::Maybe with base::Optional

headless/public/util/maybe_unittest.cc

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "headless/public/util/maybe.h"
-#include "testing/gtest/include/gtest/gtest.h"
-
-namespace headless {
-namespace {
-
-class MoveOnlyType {
- public:
-  MoveOnlyType() {}
-  MoveOnlyType(MoveOnlyType&& other) {}
-
-  void operator=(MoveOnlyType&& other) {}
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(MoveOnlyType);
-};
-
-}  // namespace
-
-TEST(MaybeTest, Nothing) {
-  Maybe<int> maybe;
-  EXPECT_TRUE(maybe.IsNothing());
-  EXPECT_FALSE(maybe.IsJust());
-}
-
-TEST(MaybeTest, Just) {
-  Maybe<int> maybe = Just(1);
-  EXPECT_FALSE(maybe.IsNothing());
-  EXPECT_TRUE(maybe.IsJust());
-  EXPECT_EQ(1, maybe.FromJust());
-
-  const Maybe<int> const_maybe = Just(2);
-  EXPECT_EQ(2, const_maybe.FromJust());
-}
-
-TEST(MaybeTest, Equality) {
-  Maybe<int> a;
-  Maybe<int> b;
-  EXPECT_EQ(a, b);
-  EXPECT_EQ(b, a);
-
-  a = Just(1);
-  EXPECT_NE(a, b);
-  EXPECT_NE(b, a);
-
-  b = Just(2);
-  EXPECT_NE(a, b);
-  EXPECT_NE(b, a);
-
-  b = Just(1);
-  EXPECT_EQ(a, b);
-  EXPECT_EQ(b, a);
-}
-
-TEST(MaybeTest, Assignment) {
-  Maybe<int> a = Just(1);
-  Maybe<int> b = Nothing<int>();
-  EXPECT_NE(a, b);
-
-  b = a;
-  EXPECT_EQ(a, b);
-}
-
-TEST(MaybeTest, MoveOnlyType) {
-  MoveOnlyType value;
-  Maybe<MoveOnlyType> a = Just(std::move(value));
-  EXPECT_TRUE(a.IsJust());
-
-  Maybe<MoveOnlyType> b = Just(MoveOnlyType());
-  EXPECT_TRUE(b.IsJust());
-
-  Maybe<MoveOnlyType> c = Nothing<MoveOnlyType>();
-  c = std::move(a);
-  EXPECT_TRUE(c.IsJust());
-
-  MoveOnlyType d = std::move(b.FromJust());
-}
-
-}  // namespace headless