Added plumbing for the availablechange event from Blink to WebPresentationClient.

Source/modules/presentation/Presentation.cpp

Index: Source/modules/presentation/Presentation.cpp
diff --git a/Source/modules/presentation/Presentation.cpp b/Source/modules/presentation/Presentation.cpp
index 93957fe0c91249fd3de4e7059667e4557ba7a0fc..660b59de0025521a53a28b209a547665c9c55b08 100644
--- a/Source/modules/presentation/Presentation.cpp
+++ b/Source/modules/presentation/Presentation.cpp
@@ -9,8 +9,12 @@
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "core/dom/DOMException.h"
+#include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
+#include "core/frame/LocalFrame.h"
 #include "modules/EventTargetModules.h"
+#include "modules/presentation/AvailableChangeEvent.h"
+#include "modules/presentation/PresentationController.h"
 
 namespace blink {
 
@@ -26,7 +30,11 @@ Presentation::~Presentation()
 // static
 Presentation* Presentation::create(ExecutionContext* executionContext)
 {
-    return new Presentation(executionContext);
+    Presentation* presentation = new Presentation(executionContext);
+    PresentationController* controller = presentation->presentationController();
+    if (controller)
+        controller->setPresentation(presentation);
+    return presentation;
 }
 
 const AtomicString& Presentation::interfaceName() const
@@ -67,4 +75,40 @@ ScriptPromise Presentation::joinSession(ScriptState* state, const String& sender
     return promise;
 }
 
+bool Presentation::addEventListener(const AtomicString& eventType, PassRefPtr<EventListener> listener, bool useCapture)
+{
+    if (eventType == EventTypeNames::availablechange) {
+        PresentationController* controller = presentationController();
+        if (controller)
+            controller->addDeviceAvailabilityListener();
+    }
+    return RefCountedGarbageCollectedEventTargetWithInlineData<Presentation>::addEventListener(eventType, listener, useCapture);
+}
+
+bool Presentation::removeEventListener(const AtomicString& eventType, PassRefPtr<EventListener> listener, bool useCapture)
+{
+    if (eventType == EventTypeNames::availablechange) {
+        PresentationController* controller = presentationController();
+        if (controller)
+            controller->removeDeviceAvailabilityListener();
+    }
+    return RefCountedGarbageCollectedEventTargetWithInlineData<Presentation>::removeEventListener(eventType, listener, useCapture);
+}
+
+void Presentation::didChangeAvailability(bool available)
+{
+    dispatchEvent(AvailableChangeEvent::create(EventTypeNames::availablechange, available));
+}
+
+PresentationController* Presentation::presentationController()
+{
+    Document* document = toDocument(executionContext());
+    if (!document)
+        return nullptr;
+    LocalFrame* frame = document->frame();
+    if (!frame)
+        return nullptr;
+    return PresentationController::from(*frame);
+}
+
 } // namespace blink