Add UMAs for checking header values against RFC 7230 in //net

This CL inserts UMAs to URLRequestHttpJob to count the number of
requests/responses that contains invalid header values in RFC 7230.
This is the first step to investigate the feasibility of updating header value
check to RFC 7230 in //net stack.

BUG=455099

Review URL: https://codereview.chromium.org/1374883002

Cr-Commit-Position: refs/heads/master@{#366563}
5 files changed