Added plumbing for the availablechange event from Blink to WebPresentationClient.

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 "public/platform/WebPresentationClient.h"
+#include "public/platform/WebPresentationController.h"
+
+namespace blink {
+
+PresentationController::PresentationController(LocalFrame& frame, WebPresentationClient* client)
+    : m_client(client)
+{
+    if (m_client)
+        m_client->setController(this);
+}
+
+PresentationController::~PresentationController()
+{
+    if (m_client)
+        m_client->setController(nullptr);
+}
+
+// static
+PassOwnPtrWillBeRawPtr<PresentationController> PresentationController::create(LocalFrame& frame, WebPresentationClient* client)
+{
+    return adoptPtrWillBeNoop(new PresentationController(frame, client));
+}
+
+// static
+const char* PresentationController::supplementName()
+{
+    return "PresentationController";
+}
+
+// static
+PresentationController* PresentationController::from(LocalFrame& frame)
+{
+    return static_cast<PresentationController*>(WillBeHeapSupplement<LocalFrame>::from(frame, supplementName()));
+}
+
+// static
+void PresentationController::provideTo(LocalFrame& frame, WebPresentationClient* client)
+{
+    WillBeHeapSupplement<LocalFrame>::provideTo(frame, PresentationController::supplementName(), PresentationController::create(frame, client));
+}
+
+void PresentationController::trace(Visitor* visitor)
+{
+    visitor->trace(m_presentation);
+    WillBeHeapSupplement<LocalFrame>::trace(visitor);
+}
+
+void PresentationController::didChangeAvailability(bool available)
+{
+    if (m_presentation)
+        m_presentation->didChangeAvailability(available);
+}
+
+void PresentationController::updateAvailableChangeWatched(bool watched)
+{
+    if (m_client)
+        m_client->updateAvailableChangeWatched(watched);
+}
+
+void PresentationController::setPresentation(Presentation* presentation)
+{
+    m_presentation = presentation;
+}
+
+} // namespace blink