[ABSL] Remove common/optional.h. (#1349)

cartographer/common/optional.h

@@ -1,69 +0,0 @@
-/*
- * Copyright 2017 The Cartographer Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef CARTOGRAPHER_COMMON_OPTIONAL_H_
-#define CARTOGRAPHER_COMMON_OPTIONAL_H_
-
-#include <memory>
-
-#include "absl/memory/memory.h"
-#include "glog/logging.h"
-
-namespace cartographer {
-namespace common {
-
-template <class T>
-class optional {
- public:
-  optional() {}
-
-  optional(const optional& other) {
-    if (other.has_value()) {
-      value_ = absl::make_unique<T>(other.value());
-    }
-  }
-
-  explicit optional(const T& value) { value_ = absl::make_unique<T>(value); }
-
-  bool has_value() const { return value_ != nullptr; }
-
-  const T& value() const {
-    CHECK(value_ != nullptr);
-    return *value_;
-  }
-
-  optional<T>& operator=(const T& other_value) {
-    this->value_ = absl::make_unique<T>(other_value);
-    return *this;
-  }
-
-  optional<T>& operator=(const optional<T>& other) {
-    if (!other.has_value()) {
-      this->value_ = nullptr;
-    } else {
-      this->value_ = absl::make_unique<T>(other.value());
-    }
-    return *this;
-  }
-
- private:
-  std::unique_ptr<T> value_;
-};
-
-}  // namespace common
-}  // namespace cartographer
-
-#endif  // CARTOGRAPHER_COMMON_OPTIONAL_H_