[PresentationAPI] Added plumbing for start/joinSession from JS to platform

Source/modules/presentation/PresentationController.cpp

Index: Source/modules/presentation/PresentationController.cpp
diff --git a/Source/modules/presentation/PresentationController.cpp b/Source/modules/presentation/PresentationController.cpp
index 5465efa84fb3c9727818a280134328be062e6675..c4a06090290159ee9f12db8493d27f093af7658c 100644
--- a/Source/modules/presentation/PresentationController.cpp
+++ b/Source/modules/presentation/PresentationController.cpp
@@ -74,6 +74,18 @@ void PresentationController::updateAvailableChangeWatched(bool watched)
         m_client->updateAvailableChangeWatched(watched);
 }
 
+void PresentationController::startSession(const String& presentationUrl, const String& presentationId, WebPresentationSessionClientCallbacks* callbacks)
+{
+    if (m_client)

[mlamouri (slow - plz ping), 2015/02/23 13:46:10]

nit: I usually recommend doing early returns instead
if (!m_client)
  return;

(you don't have to apply this change if you disagree)

[whywhat, 2015/02/25 14:11:05]

Acknowledged.

+        m_client->startSession(presentationUrl, presentationId, callbacks);
+}
+
+void PresentationController::joinSession(const String& presentationUrl, const String& presentationId, WebPresentationSessionClientCallbacks* callbacks)
+{
+    if (m_client)
+        m_client->joinSession(presentationUrl, presentationId, callbacks);

[mlamouri (slow - plz ping), 2015/02/23 13:46:10]

ditto

[whywhat, 2015/02/25 14:11:05]

Acknowledged.

+}
+
 void PresentationController::setPresentation(Presentation* presentation)
 {
     m_presentation = presentation;