Remove CallbackParamTraits and CallbackForward

They are no longer used by Callback stuff and we can replace other usage
of them with Universal References and std::forward.
This CL removes their impl and updates the use-site.

BUG=554299

Review URL: https://codereview.chromium.org/1781843003

Cr-Commit-Position: refs/heads/master@{#387435}
4 files changed