[Presentation API] Adds close method to Presentation session.

Source/modules/presentation/PresentationController.cpp

 // 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 "config.h"
 #include "modules/presentation/PresentationController.h"
 
 #include "core/frame/LocalFrame.h"
 #include "modules/presentation/PresentationSession.h"
 #include "public/platform/modules/presentation/WebPresentationClient.h"
@@ skipping 86 matching lines @@
 
 void PresentationController::joinSession(const String& presentationUrl, const String& presentationId, WebPresentationSessionClientCallbacks* callbacks)
 {
     if (!m_client) {
         delete callbacks;
         return;
     }
     m_client->joinSession(presentationUrl, presentationId, callbacks);
 }
 
+void PresentationController::closeSession(const String& url, const String& presentationId)
+{
+    if (!m_client)
+        return;
+    m_client->closeSession(url, presentationId);
+}
+
 void PresentationController::setPresentation(Presentation* presentation)
 {
     m_presentation = presentation;
 }
 
 void PresentationController::willDetachFrameHost()
 {
     if (m_client) {
         m_client->setController(nullptr);
         m_client = nullptr;
     }
 }
 
 } // namespace blink