net: remove AppendHeaderIfMissing() from HttpUtil
The last usage of this method was removed by commit 451a66360d2c: ("rlz:
get rid of the call to AppendHeaderIfMissing()").
This also made possible to remove HasHeader() as AppendHeaderIfMissing()
were the only client of it.
With removing HasHeader() method from HttpUtil we fixed the Darin's
TODO.
BUG=488593
TEST=net_unittests
R=mmenke@chromium.org
Review-Url: https://codereview.chromium.org/2624213002
Cr-Commit-Position: refs/heads/master@{#442965}
3 files changed
