Move navigation timing info to DocumentLoader

This is a preparation to not using WebURLLoader
for main resource. See step 6.d in the doc linked
to the bug.

Bug: 855189
Change-Id: Ib075d20ff2fedf655275c5fd788a83e648e4d07f
Reviewed-on: https://chromium-review.googlesource.com/c/1392744
Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620143}
6 files changed