[PresentationAPI] Implementing start/joinSession from WebPresentationClient to PresentationService.

content/renderer/presentation/presentation_session_dispatcher.cc

+// Copyright 2015 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 "content/renderer/presentation/presentation_session_dispatcher.h"
+
+#include "base/logging.h"
+
+namespace content {
+
+PresentationSessionDispatcher::PresentationSessionDispatcher(
+    presentation::PresentationSessionInfoPtr session_info)
+    : session_info_(session_info.Pass()) {
+}
+
+PresentationSessionDispatcher::~PresentationSessionDispatcher() {
+}
+
+const mojo::String& PresentationSessionDispatcher::GetUrl() const {
+  DCHECK(!session_info_.is_null());
+  return session_info_->url;
+}
+
+const mojo::String& PresentationSessionDispatcher::GetId() const {
+  DCHECK(!session_info_.is_null());
+  return session_info_->id;
+}
+
+}  // namespace content