Remove some unused includes in headless/

Bug: 
Change-Id: Icb5351bb6112fc89e36dab82c15f32887dab9217
Reviewed-on: https://chromium-review.googlesource.com/720594
Reviewed-by: David Vallet <dvallet@chromium.org>
Commit-Queue: Iris Uy <irisu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509313}
std::unique_ptr<base::DictionaryValue> CreateSuccessResponse(
    int command_id,
    std::unique_ptr<base::Value> result) {
  if (!result)
    result = base::MakeUnique<base::DictionaryValue>();

  auto response = base::MakeUnique<base::DictionaryValue>();
  response->SetInteger(kIdParam, command_id);
  response->Set(kResultParam, std::move(result));
  return response;
}

std::unique_ptr<base::DictionaryValue> CreateSuccessResponse(
    int command_id,
    std::unique_ptr<base::Value> result) {
  if (!result)
    result = base::MakeUnique<base::DictionaryValue>();

  auto response = base::MakeUnique<base::DictionaryValue>();
  response->SetInteger(kIdParam, command_id);
  response->Set(kResultParam, std::move(result));
  return response;
}
