Migrate TranslateScript and TranslateURLFetcher away from base::Bind

Driven by CL, preparation for CL https://crrev.com/c/1085947.

BUG=714018

Change-Id: I455fb3bfc2addd6b99151778639f47de4d240709
Reviewed-on: https://chromium-review.googlesource.com/1085948
Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Cr-Commit-Position: refs/heads/master@{#564437}
3 files changed