Add skeleton webrtc::SessionDescription and webrtc::MediaDescription classes.

BUG=webrtc:7311

Review-Url: https://codereview.webrtc.org/2743003004
Cr-Commit-Position: refs/heads/master@{#17181}

webrtc/api/ortc/mediadescription.cc

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+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/api/ortc/mediadescription.h"
+
+namespace webrtc {}

webrtc/api/ortc/mediadescription.h

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+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_API_ORTC_MEDIADESCRIPTION_H_
+#define WEBRTC_API_ORTC_MEDIADESCRIPTION_H_
+
+#include <string>
+#include <utility>
+
+#include "webrtc/base/optional.h"
+
+namespace webrtc {
+
+// A structured representation of a media description within an SDP session
+// description.
+class MediaDescription {
+ public:
+  explicit MediaDescription(std::string mid) : mid_(std::move(mid)) {}
+
+  ~MediaDescription() {}
+
+  // The mid(media stream identification) is used for identifying media streams
+  // within a session description.
+  // https://tools.ietf.org/html/rfc5888#section-6
+  rtc::Optional<std::string> mid() const { return mid_; }
+  void set_mid(std::string mid) { mid_.emplace(std::move(mid)); }
+
+ private:
+  rtc::Optional<std::string> mid_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_API_ORTC_MEDIADESCRIPTION_H_

webrtc/api/ortc/mediadescription_unittest.cc

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+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/api/ortc/mediadescription.h"
+#include "webrtc/test/gtest.h"
+
+namespace webrtc {
+
+class MediaDescriptionTest : public testing::Test {};
+
+TEST_F(MediaDescriptionTest, CreateMediaDescription) {
+  MediaDescription m("a");
+  EXPECT_EQ("a", m.mid());
+}
+}

webrtc/api/ortc/sessiondescription.cc

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+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/api/ortc/sessiondescription.h"
+
+namespace webrtc {}

webrtc/api/ortc/sessiondescription.h

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+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_API_ORTC_SESSIONDESCRIPTION_H_
+#define WEBRTC_API_ORTC_SESSIONDESCRIPTION_H_
+
+#include <string>
+#include <utility>
+
+namespace webrtc {
+
+// A structured representation of an SDP session description.
+class SessionDescription {
+ public:
+  SessionDescription(std::string session_id, std::string session_version)
+      : session_id_(std::move(session_id)),
+        session_version_(std::move(session_version)) {}
+
+  // https://tools.ietf.org/html/rfc4566#section-5.2
+  // o=<username> <sess-id> <sess-version> <nettype> <addrtype>
+  //   <unicast-address>
+  // session_id_ is the "sess-id" field.
+  // session_version_ is the "sess-version" field.
+  const std::string& session_id() const { return session_id_; }
+  void set_session_id(std::string session_id) {
+    session_id_ = std::move(session_id);
+  }
+
+  const std::string& session_version() const { return session_version_; }
+  void set_session_version(std::string session_version) {
+    session_version_ = std::move(session_version);
+  }
+
+ private:
+  std::string session_id_;
+  std::string session_version_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_API_ORTC_SESSIONDESCRIPTION_H_

webrtc/api/ortc/sessiondescription_unittest.cc

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+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/api/ortc/sessiondescription.h"
+#include "webrtc/test/gtest.h"
+
+namespace webrtc {
+
+class SessionDescriptionTest : public testing::Test {};
+
+TEST_F(SessionDescriptionTest, CreateSessionDescription) {
+  SessionDescription s("a", "0");
+  EXPECT_EQ("a", s.session_id());
+  EXPECT_EQ("0", s.session_version());
+}
+}