(let* ((query "test")
       (url-request-method "GET")
       (random-id (format "%016x" (random (expt 16 16))))
       (expiration (format-time-string "%a, %d %b %Y %H:%M:%S.00 %Z"
                                       (time-add (current-time)
                                                 (seconds-to-time 3600)) t))
       (my-cookie (mapconcat #'identity
                             (list (format "GSP=ID=%s:CF=4; " random-id)
                                   (format "expires=%s" expiration)
                                   "path=/"
                                   "domain=scholar.google.com")
                             "; "))
       (url-current-object
        (url-generic-parse-url "http://scholar.google.com")))
  
  (url-cookie-handle-set-cookie my-cookie)
  ;; (gscholar-bibtex--url-retrieve-as-string
  ;;  (concat "http://scholar.google.com/scholar?q="
  ;;          (url-hexify-string
  ;;           (replace-regexp-in-string " " "\+" query))))
  )

The above block changes url-cookie-storage as

(("scholar.google.com"
  [url-cookie "GSP" "ID=3b42efa2a3173e2b:CF=4" "Fri, 30 Sep 2016 10:40:35.00 UTC" "/" "scholar.google.com" nil]))

When I uncomment the (gscholar-bibtex--url-retrieve-as-string ...) part (after clearing up (setq url-cookie-storage nil)), url-cookie-storage changes to

(("scholar.google.com"
  [url-cookie "GSP" "LM=1475228728:S=6n6XaGoLKYDaGo6s" "30-Sep-2018 09:45:28.00 GMT" "/" "scholar.google.com" nil])
 (".google.com"
  [url-cookie "HttpOnly" nil "01-Apr-2017 09:45:28.00 GMT" "/" ".google.com" nil]
  [url-cookie "NID" "87=gKaRWnrelO6mO3-jApeDc4WJdqQRVxJ7IhdZcMTqX8Hwdtpog_VIILSGx5Oae-SU9SsxP5aAHUUymmNOamOxGKWLqFLF2mYE_a8lF7pPpgbnLzOtC7X_ZHKr2TmROuMe" "01-Apr-2017 09:45:28.00 GMT" "/" ".google.com" nil]))

The retrived url result is pasted in 2016-09-30_url.txt