[Presentation API] Added the DefaultPresentationStart event and parsing of the default presentation…

Source/modules/presentation/DefaultPresentationStartEvent.h

+// 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.
+
+#ifndef DefaultPresentationStartEvent_h
+#define DefaultPresentationStartEvent_h
+
+#include "modules/EventModules.h"
+#include "modules/presentation/DefaultPresentationStartEventInit.h"
+#include "modules/presentation/PresentationSession.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+// DefaultPresentationStartEvent object definition corresponding to the event
+// IDL from the Presentation API,
+// see https://code.google.com/p/chromium/issues/detail?id=459001 for details.

[Peter Beverloo, 2015/03/03 21:19:24]

I don't think this comment is useful at all. Instead, could you have the comment
say that the event is used for? For example:

// Presentation API event to be fired when a presentation has been triggered
// by the embedder for the default presentation URL.

[whywhat, 2015/03/05 18:41:46]

Done.

+class DefaultPresentationStartEvent final : public Event {

[mark a. foltz, 2015/03/05 19:44:11]

Why "DefaultPresentationStart?"  The purpose of the event is to convey to the
page a specific PresentationSession, and we say "startSession" instead of
"startPresentation."  So I would suggest "DefaultSessionStart" instead.

[whywhat, 2015/03/05 20:46:02]

Yes, I think using session is more consistent. However, neither default session
nor default presentation seem to be valid terms: in "Default Presentation URL"
the url is default, not the presentation/session. Since it designates an
automatic session launch by the browser, Maybe |autosessionstart|?

Probably late but I also realize that having sessions is more of an
implementation detail and a bit redundant in the spec so we could have chosen
simpler names like navigator.presentation.start/join/onautostart/etc

+    DEFINE_WRAPPERTYPEINFO();
+public:
+    virtual ~DefaultPresentationStartEvent();
+
+    static PassRefPtrWillBeRawPtr<DefaultPresentationStartEvent> create()
+    {
+        return adoptRefWillBeNoop(new DefaultPresentationStartEvent);
+    }
+    static PassRefPtrWillBeRawPtr<DefaultPresentationStartEvent> create(const AtomicString& eventType, PresentationSession* session)
+    {
+        return adoptRefWillBeNoop(new DefaultPresentationStartEvent(eventType, session));
+    }
+    static PassRefPtrWillBeRawPtr<DefaultPresentationStartEvent> create(const AtomicString& eventType, const DefaultPresentationStartEventInit& initializer)
+    {
+        return adoptRefWillBeNoop(new DefaultPresentationStartEvent(eventType, initializer));
+    }
+
+    PresentationSession& session() { return *m_session; }

[Peter Beverloo, 2015/03/03 21:19:24]

You probably want to gracefully handle m_session being NULL, given that not all
the constructors actually create one. (Return a pointer instead.)

Consider this JavaScript snippet:

var event = document.createEvent('defaultpresentationstart', { .. });
event.session; // boom

[whywhat, 2015/03/05 18:41:46]

Done.

+
+    virtual const AtomicString& interfaceName() const override;
+
+private:
+    DefaultPresentationStartEvent();
+    DefaultPresentationStartEvent(const AtomicString& eventType, PresentationSession*);
+    DefaultPresentationStartEvent(const AtomicString& eventType, const DefaultPresentationStartEventInit& initializer);
+
+    Persistent<PresentationSession> m_session;
+};
+
+DEFINE_TYPE_CASTS(DefaultPresentationStartEvent, Event, event, event->interfaceName() == EventNames::DefaultPresentationStartEvent, event.interfaceName() == EventNames::DefaultPresentationStartEvent);
+
+} // namespace blink
+
+#endif // DefaultPresentationStartEvent_h