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..b4a6da06f776fd5145f76394ea5a37fafcee062b 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 {
 
@@ -21,12 +25,19 @@ Presentation::Presentation(ExecutionContext* executionContext)
 
 Presentation::~Presentation()
 {
+    PresentationController* controller = presentationController();
+    if (controller)
+        controller->setPresentation(nullptr);
 }
 
 // static
 Presentation* Presentation::create(ExecutionContext* executionContext)
 {
-    return new Presentation(executionContext);
+    Presentation* presentation = new Presentation(executionContext);
+    PresentationController* controller = presentation->presentationController();
+    if (controller)
+        controller->setPresentation(presentation);

[Peter Beverloo, 2015/01/07 14:29:08]

When is it valid for the runtime Presentation flag to be enabled, but not having
had a WebPresentationClient provided by the embedder? It seems to me like
presentationController() can ASSERT and return a reference instead.

[whywhat, 2015/01/07 16:22:16]

I imagined a hypothetical situation where the UA might run on hardware that
doesn't support screen discovery/presenting and decided to be on the safe side.

[Peter Beverloo, 2015/01/07 19:53:11]

In that case we wouldn't enable the run-time flag, causing the entire feature to
not be exposed. If the run-time flag is enabled, it's fair to ASSERT existence
of the PresentationController.

[whywhat, 2015/01/08 16:05:28]

Done.

+    return presentation;
 }
 
 const AtomicString& Presentation::interfaceName() const
@@ -67,4 +78,44 @@ 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::deviceAvailabilityChanged(bool available)

[Peter Beverloo, 2015/01/07 14:29:08]

Why is this called "deviceAvailabilityChanged" while the event is
"availablechanged"? Usually methods like this are called something like
"didChangeAvailability".

[whywhat, 2015/01/07 16:22:16]

Done.

+{
+    dispatchEvent(AvailableChangeEvent::create(EventTypeNames::availablechange, available));
+}
+
+PresentationController* Presentation::presentationController()
+{
+    if (!frame())

[Peter Beverloo, 2015/01/07 14:29:08]

Rather than having a separate frame() method, could you just inline it and have
a local LocalFrame* variable?

[whywhat, 2015/01/07 16:22:16]

Done.

+        return nullptr;
+    return PresentationController::from(*frame());
+}
+
+LocalFrame* Presentation::frame()
+{
+    Document* document = toDocument(executionContext());
+    if (document)
+        return document->frame();
+    return nullptr;
+}
+
 } // namespace blink