Compatibility issue with Chrome 71 (2018-12-04)

[tmorton]

It seems like the Chrome DevTools protocol has changed, so this library will no longer work with Chrome 71. I haven't found a work-around. I'm just documenting this to save others the trouble.

I believe the problem is that Chrome has stopped accepting the Target.createBrowserContext message. There isn't any documentation about a change, but several similar projects have this problem: wirepair/gcd#24 and chromedp/chromedp#244

Here's the symptoms:

iex(1)> HPDF.print_pdf!("https://google.com")
** (exit) exited in: GenServer.call(#PID<0.392.0>, {:print_pdf, "https://google.com", []}, :infinity)
    ** (EXIT) exited in: GenServer.call(HPDF.Browser, :new_session, 5000)
        ** (EXIT) time out
    (elixir) lib/gen_server.ex:831: GenServer.call/3
    (hpdf) lib/hpdf/controller.ex:22: HPDF.Controller.print_pdf!/2
iex(1)> [error] GenServer #PID<0.392.0> terminating
** (stop) exited in: GenServer.call(HPDF.Browser, :new_session, 5000)
    ** (EXIT) time out
    (elixir) lib/gen_server.ex:831: GenServer.call/3
    (hpdf) lib/hpdf/controller.ex:28: HPDF.Controller.handle_call/3
    (stdlib) gen_server.erl:636: :gen_server.try_handle_call/4
    (stdlib) gen_server.erl:665: :gen_server.handle_msg/6
    (stdlib) proc_lib.erl:247: :proc_lib.init_p_do_apply/3
Last message (from #PID<0.390.0>): {:print_pdf, "https://google.com", []}
State: %{}
Client #PID<0.390.0> is alive
    (stdlib) gen.erl:169: :gen.do_call/4
    (elixir) lib/gen_server.ex:828: GenServer.call/3
    (hpdf) lib/hpdf/controller.ex:22: HPDF.Controller.print_pdf!/2
    (stdlib) erl_eval.erl:670: :erl_eval.do_apply/6
    (elixir) src/elixir.erl:233: :elixir.eval_forms/4
    (iex) lib/iex/evaluator.ex:245: IEx.Evaluator.handle_eval/5
    (iex) lib/iex/evaluator.ex:225: IEx.Evaluator.do_eval/3
    (iex) lib/iex/evaluator.ex:203: IEx.Evaluator.eval/3
    (iex) lib/iex/evaluator.ex:89: IEx.Evaluator.loop/1
    (iex) lib/iex/evaluator.ex:24: IEx.Evaluator.init/4
    (stdlib) proc_lib.erl:247: :proc_lib.init_p_do_apply/3