HTTP2 implementation returns PUSH PROMISES for frames that are already a promise (even id)

if (request.getServletPath().endsWith(".html") || request.getPathInfo().endsWith(".html")) {
            PushBuilder pushBuilder = request.newPushBuilder();
            if (pushBuilder != null) {
                // pushing css and js in advance
                pushBuilder.path("resources/one.css").push();
                pushBuilder.path("resources/one.js").push();
            }
            // slow the index to let chrome to receive the invalid push promise
            try {Thread.sleep(1000L);} catch (InterruptedException e) {}
            getServletContext()
                    .getRequestDispatcher("/WEB-INF/index.html")
                    .forward(request, response);
        } else if (request.getPathInfo().endsWith(".css")) {
            PushBuilder pushBuilder = request.newPushBuilder();
            if (pushBuilder != null) {
                // pushing images in advance
                pushBuilder.path("resources/one.png").push();
            }
            getServletContext()
                    .getRequestDispatcher("/WEB-INF/sample.css")
                    .forward(request, response);
        } else if (request.getPathInfo().endsWith(".js")) {
            getServletContext()
                    .getRequestDispatcher("/WEB-INF/sample.js")
                    .forward(request, response);
        } else if (request.getPathInfo().endsWith(".png")) {
            getServletContext()
                    .getRequestDispatcher("/WEB-INF/sample.png")
                    .forward(request, response);
        } else {
            throw new ServletException("Invalid request");
        }