Revert "Don't adjust the NavigationTimings on redirects"

This reverts commit aeecb4f32ece14a8a294e4f9b80a5bb2278091c9.

Reason for revert: Causing lots of failures on webkit bots, e.g.:
https://ci.chromium.org/buildbot/chromium.webkit/WebKit%20Linux%20Trusty/42143

Original change's description:
> Don't adjust the NavigationTimings on redirects
>
> We adjust the timings in WebDocumentLoaderImpl::UpdateNavigation(),
> shouldn't update in each AddRedirect() (which is called in a batch
> way after all the redirects are handled in the browser process with PlzNavigate,
> adjusting timings there with current timestamp is totally wrong)
>
> R=​ksakamoto,arthursonzogni
>
> Bug: 813889
> Change-Id: I3a57d3fdf1833c300feb5ee61737b64cece0946b
> Reviewed-on: https://chromium-review.googlesource.com/974673
> Reviewed-by: Kunihiko Sakamoto <ksakamoto@chromium.org>
> Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#546001}

TBR=kinuko@chromium.org,ksakamoto@chromium.org,arthursonzogni@chromium.org

Change-Id: I467ed888084ea0eda06faa903d1797fabffc47da
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 813889
Reviewed-on: https://chromium-review.googlesource.com/981912
Reviewed-by: Ben Wells <benwells@chromium.org>
Commit-Queue: Ben Wells <benwells@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546025}

navigation-timing/test_timing_server_redirect.html

@@ -32,7 +32,6 @@
                 test_timing_order('redirectStart', 'navigationStart');
                 test_timing_order('redirectEnd', 'redirectStart');
                 test_timing_order('fetchStart', 'redirectEnd');
-                test_timing_order('requestStart', 'fetchStart');
             }
         </script>