Define push_messaging module with PushManager skeleton.

Source/modules/push_messaging/PushManager.h

+// Copyright 2014 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 PushManager_h
+#define PushManager_h
+
+#include "bindings/v8/ScriptWrappable.h"
+#include "wtf/RefCounted.h"
+#include "wtf/text/WTFString.h"
+
+namespace WebCore {
+
+class ExecutionContext;
+class ScriptPromise;
+
+class PushManager FINAL : public RefCountedWillBeRefCountedGarbageCollected<PushManager>, public ScriptWrappable {
+public:
+    static PassRefPtrWillBeRawPtr<PushManager> create() { return adoptRefWillBeNoop(new PushManager()); }
+    virtual ~PushManager();
+
+    ScriptPromise registerPushMessaging(ExecutionContext*, const String& senderId);
+
+private:
+    PushManager();
+};
+
+} // namespace WebCore
+
+#endif // PushManager_h