[Findit] Make sure pass in empty headers instead of None when no particular headers needed in http_requests.
[Findit] Make sure pass in empty headers instead of None when no particular headers needed in http_requests.

Review URL: https://codereview.chromium.org/1287303003

nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra