Remove features::kCrossSiteDocumentBlocking...

Cross-Origin Read Blocking (CORB) was enabled by default in 68.0.3410.0.
Since this feature has shipped quite a while ago, it seems that now is a
good time to remove the code responsible for enabling/disabling the
feature.

Bug: 802835
Change-Id: I11b3058447607b31cb27a3e7dbc8db137411d7b8
Reviewed-on: https://chromium-review.googlesource.com/1228485
Reviewed-by: Charlie Reis <creis@chromium.org>
Commit-Queue: Ɓukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592840}
6 files changed