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

Source/modules/presentation/PresentationSessionClientCallbacks.h

Index: Source/modules/presentation/PresentationSessionClientCallbacks.h
diff --git a/Source/modules/presentation/PresentationSessionClientCallbacks.h b/Source/modules/presentation/PresentationSessionClientCallbacks.h
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+++ b/Source/modules/presentation/PresentationSessionClientCallbacks.h
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+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PresentationSessionClientCallbacks_h
+#define PresentationSessionClientCallbacks_h
+
+#include "platform/heap/Handle.h"
+#include "public/platform/modules/presentation/WebPresentationClient.h"
+#include "wtf/Noncopyable.h"
+#include "wtf/PassRefPtr.h"
+#include "wtf/RefPtr.h"
+
+namespace blink {
+
+class Presentation;
+class ScriptPromiseResolver;
+
+// The implementation of the WebCallbacks interface passed to the embedder to
+// get the result of start/joinSession() calls. Will in its turn resolve the
+// corresponding Promise given to the frame.
+// When creating the session succeeds, onSuccess() is invoked with the
+// implementation of the WebPresentationSessionClient interface. If creating the
+// session fails, onError() is invoked with the implementation of the
+// WebPresentationError interface.
+// Owned by the receiver of the callback and must be deleted after use.
+class PresentationSessionClientCallbacks final : public WebPresentationSessionClientCallbacks {
+    WTF_MAKE_NONCOPYABLE(PresentationSessionClientCallbacks);
+public:
+    PresentationSessionClientCallbacks(PassRefPtrWillBeRawPtr<ScriptPromiseResolver>, Presentation*);
+    virtual ~PresentationSessionClientCallbacks();
+
+    // WebPresentationSessionClientCallbacks implementation.
+    virtual void onSuccess(WebPresentationSessionClient*) override;
+    virtual void onError(WebPresentationError*) override;
+
+private:
+    RefPtrWillBePersistent<ScriptPromiseResolver> m_resolver;
+    Persistent<Presentation> m_presentation;
+};
+
+} // namespace blink
+
+#endif // PresentationSessionClientCallbacks_h