Add the Presentation API module and a single event target

Source/modules/presentation/NavigatorPresentation.cpp

+// 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.
+
+#include "config.h"
+#include "modules/presentation/NavigatorPresentation.h"
+
+#include "core/dom/Document.h"

[Peter Beverloo, 2014/07/25 18:01:17]

nit: This seems to be unused.

[whywhat, 2014/08/19 18:07:34]

It's needed for the compiler to know that Document* returned by document() can
be converted to ExecutionContext since it inherits from it. 

+#include "core/frame/LocalFrame.h"
+#include "core/frame/Navigator.h"
+#include "modules/presentation/Presentation.h"

[Peter Beverloo, 2014/07/25 18:01:17]

nit: You include this in the header.

[whywhat, 2014/08/19 18:07:34]

Done.

+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+NavigatorPresentation::NavigatorPresentation(LocalFrame* frame)
+    : DOMWindowProperty(frame)
+{
+}
+
+NavigatorPresentation::~NavigatorPresentation()
+{
+}
+
+// static
+const char* NavigatorPresentation::supplementName()
+{
+    return "NavigatorPresentation";
+}
+
+// static
+NavigatorPresentation& NavigatorPresentation::from(Navigator& navigator)
+{
+    NavigatorPresentation* supplement = static_cast<NavigatorPresentation*>(WillBeHeapSupplement<Navigator>::from(navigator, supplementName()));
+    if (!supplement) {
+        supplement = new NavigatorPresentation(navigator.frame());
+        provideTo(navigator, supplementName(), adoptPtrWillBeNoop(supplement));
+    }
+    return *supplement;
+}
+
+// static
+Presentation& NavigatorPresentation::presentation(Navigator& navigator)
+{
+    return NavigatorPresentation::from(navigator).presentation();
+}
+
+Presentation& NavigatorPresentation::presentation()
+{
+    ASSERT(frame());

[Peter Beverloo, 2014/07/25 18:01:17]

Actually, I think frame() can return NULL when a document creates an iframe in
the same origin, gets a reference to the |navigator| instance of that document,
and then accesses the |presentation| property on it..

[whywhat, 2014/08/19 18:07:34]

So how do I create a presentation object then? Or should I revert presentation()
to return a pointer and return NULL in the case you describe?

+    if (!m_presentation)
+        m_presentation = Presentation::create(frame());
+    return *m_presentation.get();
+}
+
+void NavigatorPresentation::trace(Visitor* visitor)
+{
+    visitor->trace(m_presentation);
+    WillBeHeapSupplement<Navigator>::trace(visitor);
+}
+
+} // namespace blink