Revise TLS 1.3 downgrade feature and metrics.
Due to non-compliant middleboxes, it is possible we'll need to do some
surgery to this mechanism. Fix the double-negative on the base::Feature
so it is less confusing and gather more extensive metrics when
enforcement is disabled. Also flip the default in trunk to disabled and
connect it to about:flags.
Finally, add a bunch of machinery to test this stuff.
Bug: boringssl:226
Change-Id: Ib910328c9733b47db16b4cb811e8f2cb09b69d0c
Reviewed-on: https://chromium-review.googlesource.com/c/1274605
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Steven Valdez <svaldez@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#599879}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 570460e9b6482055b236a8b60ef5521506bf991c4 files changed
