Web tests: always dump didStartProvisionalLoad

This brings two benefits:
- Dump what we actually call on RenderFrameObservers.
- Remove dependency on DocumentLoader::GetRequest which goes away
  (see the doc linked to bug).

Bug: 855189
Change-Id: I7c869d870dcb2d51cddea1998335af0e6162af5e
Reviewed-on: https://chromium-review.googlesource.com/c/1390237
Reviewed-by: Nate Chapin <japhet@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620129}
30 files changed