Add mechanism to trim HTTP response headers

Add mechanism to trim HTTP response headers

The main motivation for this is to drop headers like
"content-security-policy", which are known to cause problems
with script injections in sites with strict policies.

R=nednguyen@google.com
BUG=#72

[nickie, 2016-05-10 17:09:33]

This patch installs the mechanism for trimming response headers and actually
trims "content-security-policy".  This is what we (v8-team-muc) would want for
benchmarking purposes.  It may be desirable, however, to control this trimming
with a flag, or even to expose a more generic mechanism for determining what is
to be trimmed and what not.

[nednguyen, 2016-05-11 21:52:44]

Can you add test coverage?

[nickie, 2016-05-12 14:25:13]

On 2016/05/11 21:52:44, nednguyen wrote:
> Can you add test coverage?

I added a test similar to the existing one for testing the trimming of request
headers.  Let me know if something else is needed.

[nednguyen, 2016-05-13 17:14:32]

lgtm

[nednguyen, 2016-05-13 17:16:49]

On 2016/05/13 17:14:32, nednguyen wrote:
> lgtm

Thanks for your work, this is landed in
https://github.com/chromium/web-page-replay/commit/d23e5a88d82d1e1f6ce759f701...