[Presentation API] Adds close method to Presentation session.

Source/modules/presentation/PresentationSession.h

 // Copyright 2014 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.
 
 #ifndef PresentationSession_h
 #define PresentationSession_h
 
 #include "core/events/EventTarget.h"
 #include "core/frame/DOMWindowProperty.h"
 #include "wtf/text/AtomicString.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class Presentation;
+class PresentationController;
 class WebPresentationSessionClient;
 class WebString;
 
 class PresentationSession final
     : public RefCountedGarbageCollectedEventTargetWithInlineData<PresentationSession>
     , public DOMWindowProperty {
     DEFINE_EVENT_TARGET_REFCOUNTING_WILL_BE_REMOVED(RefCountedGarbageCollected<PresentationSession>);
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(PresentationSession);
     DEFINE_WRAPPERTYPEINFO();
 public:
@@ skipping 12 matching lines @@
 
     void postMessage(const String& message);
     void close();
 
     DEFINE_ATTRIBUTE_EVENT_LISTENER(message);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(statechange);
 
 private:
     PresentationSession(LocalFrame*, const WebString& id);
 
+    // Returns the |PresentationController| object associated with the frame |Presentation| corresponds to.

[whywhat, 2015/03/17 23:35:19]

nit: Although Blink doesn't yet have line length limit, it doesn't forbid to
limit comments to 80 chars (unlike method prototypes, for example). I think
keeping this comment in 80 chars would make the reviews/reading the code
relatively easier.

[haibinlu, 2015/03/18 00:58:23]

Done.

+    // Can return |nullptr| if the frame is detached from the document.
+    PresentationController* presentationController();
+
     String m_id;
     AtomicString m_state;
 };
 
 } // namespace blink
 
 #endif // PresentationSession_h