[Presentation API] Added the DefaultPresentationStart event and parsing of the default presentation…

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 3b0c26cc2850685fde0b097d2223cd9fd8df2522..b5ccfa76bb74b0225a7e1cdb372ea23179f5a159 100644
--- a/Source/modules/presentation/PresentationController.cpp
+++ b/Source/modules/presentation/PresentationController.cpp
@@ -6,6 +6,7 @@
 #include "modules/presentation/PresentationController.h"
 
 #include "core/frame/LocalFrame.h"
+#include "modules/presentation/PresentationSession.h"
 #include "public/platform/modules/presentation/WebPresentationClient.h"
 
 namespace blink {
@@ -74,6 +75,17 @@ void PresentationController::updateAvailableChangeWatched(bool watched)
         m_client->updateAvailableChangeWatched(watched);
 }
 
+void PresentationController::didStartDefaultSession(WebPresentationSessionClient* sessionClient)
+{
+    if (!m_presentation) {
+        PresentationSession::dispose(sessionClient);
+        return;
+    }
+
+    PresentationSession* session = PresentationSession::take(sessionClient, m_presentation);
+    m_presentation->didStartDefaultSession(session);
+}
+
 void PresentationController::startSession(const String& presentationUrl, const String& presentationId, WebPresentationSessionClientCallbacks* callbacks)
 {
     if (!m_client) {