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

Source/modules/presentation/PresentationSession.cpp

Index: Source/modules/presentation/PresentationSession.cpp
diff --git a/Source/modules/presentation/PresentationSession.cpp b/Source/modules/presentation/PresentationSession.cpp
index a7920a0747f08f762c06e42e10cc656b282f16e3..78d1c804fda6ec64c2e7825fa942aff2877d08b3 100644
--- a/Source/modules/presentation/PresentationSession.cpp
+++ b/Source/modules/presentation/PresentationSession.cpp
@@ -5,12 +5,17 @@
 #include "config.h"
 #include "modules/presentation/PresentationSession.h"
 
+#include "core/dom/Document.h"
+#include "core/frame/LocalFrame.h"
 #include "modules/EventTargetModules.h"
+#include "public/platform/WebString.h"
 
 namespace blink {
 
-PresentationSession::PresentationSession(ExecutionContext* executionContext)
-    : ContextLifecycleObserver(executionContext)
+PresentationSession::PresentationSession(LocalFrame* frame, const WebString& id)
+    : DOMWindowProperty(frame)
+    , m_id(id)
+    , m_state("disconnected")
 {
 }
 
@@ -19,9 +24,9 @@ PresentationSession::~PresentationSession()
 }
 
 // static
-PresentationSession* PresentationSession::create(ExecutionContext* executionContext)
+PresentationSession* PresentationSession::create(LocalFrame* frame, const WebString& id)
 {
-    return new PresentationSession(executionContext);
+    return new PresentationSession(frame, id);
 }
 
 const AtomicString& PresentationSession::interfaceName() const
@@ -31,13 +36,14 @@ const AtomicString& PresentationSession::interfaceName() const
 
 ExecutionContext* PresentationSession::executionContext() const
 {
-    return ContextLifecycleObserver::executionContext();
-}
+    if (!frame())
+        return nullptr;
+    return frame()->document();}
 
 DEFINE_TRACE(PresentationSession)
 {
     RefCountedGarbageCollectedEventTargetWithInlineData<PresentationSession>::trace(visitor);
-    ContextLifecycleObserver::trace(visitor);
+    DOMWindowProperty::trace(visitor);
 }
 
 void PresentationSession::postMessage(const String& message)