[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)
+        m_client->startSession(presentationUrl, presentationId, callbacks);

[mlamouri (slow - plz ping), 2015/02/25 20:51:06]

Hmm, sorry for realizing that now, but you have to |delete callbacks;| if there
is no |m_client|, otherwise, you are leaking that.

Maybe something like:
if (!m_client) {
  delete callbacks;
  return;
}
m_client->...

[whywhat, 2015/02/25 21:04:14]

I start thinking I need a ref-counted pointer here...

[mlamouri (slow - plz ping), 2015/02/25 21:08:54]

There is no ref pointer that crosses Blink/Chromium boundary.

[whywhat, 2015/02/25 22:46:51]

Something simple like std::unique_ptr would work in this case. It seems Blink
lacks such a pointer and RefPtr is too much :(

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

[mlamouri (slow - plz ping), 2015/02/25 20:51:06]

ditto

[whywhat, 2015/02/25 22:46:52]

Done.

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