Show bad feature flag infobar for SignedHTTPExchange

Screenshot: https://crbug.com/803774#c41
Bug: 803774

Change-Id: I3cffd4258de124df22f4bc7560e0e9dbc91ca442
Reviewed-on: https://chromium-review.googlesource.com/956654
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Tommy Martino <tmartino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542990}
6 files changed