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

Source/modules/presentation/DefaultSessionStartEventInit.idl

Index: Source/modules/presentation/DefaultSessionStartEventInit.idl
diff --git a/Source/modules/app_banner/BeforeInstallPromptEventInit.idl b/Source/modules/presentation/DefaultSessionStartEventInit.idl
similarity index 65%
copy from Source/modules/app_banner/BeforeInstallPromptEventInit.idl
copy to Source/modules/presentation/DefaultSessionStartEventInit.idl
index 5fac0385bbc7f9eb5d4ec14dee29c984c248d400..231da6794037979aa98e411aa0ff0cbdd85fbd01 100644
--- a/Source/modules/app_banner/BeforeInstallPromptEventInit.idl
+++ b/Source/modules/presentation/DefaultSessionStartEventInit.idl
@@ -2,6 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-dictionary BeforeInstallPromptEventInit : EventInit {
-    DOMString platform = "web";
-};
+dictionary DefaultSessionStartEventInit : EventInit {
+    PresentationSession session;
+};