GitLab

- use EmbeddedTestServer instead of web::HttpServer
- do not assert inside test helpers
- inherit fixture from WebTestWithWebState
- replace deprecated base::test::ios::WaitUntilCondition
  with testing::WaitUntilConditionOrTimeout

Bug=None

Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I3e7fbd67193f68fc5575fc529a7ac1f80d89126c
Reviewed-on: https://chromium-review.googlesource.com/1055777Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558366}