[iOS] Delete LegacyFullscreenController.

This is patch 1 of a 3-way patch.

Bug: 798064
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I2df80fc63af54f71a167dc986da5527b62c88016
Reviewed-on: https://chromium-review.googlesource.com/912238
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Kurt Horimoto <kkhorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535890}
47 files changed