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

Source/modules/presentation/PresentationController.h

Index: Source/modules/presentation/PresentationController.h
diff --git a/Source/modules/presentation/PresentationController.h b/Source/modules/presentation/PresentationController.h
index ac5879ecae4052a942ff1faa58c77517130e186c..f7cf607bfa62f2b731853f493abd5ffa9cb8a5f8 100644
--- a/Source/modules/presentation/PresentationController.h
+++ b/Source/modules/presentation/PresentationController.h
@@ -15,6 +15,7 @@
 namespace blink {
 
 class LocalFrame;
+class PresentationSession;
 
 // The coordinator between the various page exposed properties and the content
 // layer represented via |WebPresentationClient|.
@@ -41,11 +42,17 @@ public:
     // Implementation of WebPresentationController.
     virtual void didChangeAvailability(bool available) override;
     virtual bool isAvailableChangeWatched() const override;
+    virtual void didStartDefaultPresentation(WebPresentationSessionClient*) override;
+    virtual bool isDefaultPresentationStartWatched() const override;
 
     // Called when the first listener was added to or the last listener was removed from the
     // |availablechange| event.
     void updateAvailableChangeWatched(bool watched);
 
+    // Called when the first listener was added to or the last listener was removed from the
+    // |defaultpresentationstart| event.
+    void updateDefaultPresentationStartWatched(bool watched);
+
     // Called when the frame wants to start a new presentation.
     void startSession(const String& presentationUrl, const String& presentationId, WebPresentationSessionClientCallbacks*);