Actually, we should probably enable it on all the amd64 builders.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/bc5e8da08c83c08729728e50bcba23f1bb7fb52b

commit bc5e8da08c83c08729728e50bcba23f1bb7fb52b
Author: Caroline Tice <cmtice@google.com>
Date: Sun Jun 10 00:51:46 2018

Enable CFI on Chrome for AMD64 boards.

We have enabled CFI on the caroline & terra release builders for
a while now, and we have tested CFI on all the rest of the AMD64
board families.  This will enable CFI on all the AMD64 builds in
Chrome OS.

NOTE:  This CL should wait until the new LLVM compiler has been
in place for about a week (June 11?), before being committed.

BUG= chromium:828593 
TEST=Tested all amd64 boards with CFI enabled.  See the
test spreadsheet at
https://docs.google.com/spreadsheets/d/1pkhgvgfifD9tUGgA4ip5D5EAQE7CYJ10GXFE975ZdWw/edit?usp=sharing

Change-Id: I31bb191244433a87e13e9b02a081de8d12c7e57c
Reviewed-on: https://chromium-review.googlesource.com/1085479
Reviewed-by: Yunlian Jiang <yunlian@chromium.org>
Commit-Queue: Yunlian Jiang <yunlian@chromium.org>
Tested-by: Yunlian Jiang <yunlian@chromium.org>
Trybot-Ready: Yunlian Jiang <yunlian@chromium.org>

[modify] https://crrev.com/bc5e8da08c83c08729728e50bcba23f1bb7fb52b/profiles/arch/amd64/package.use

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/863eebc081b86e7d830b6dfb8200be80cb27959c

commit 863eebc081b86e7d830b6dfb8200be80cb27959c
Author: Yunlian Jiang <yunlian@google.com>
Date: Sun Jun 10 02:17:23 2018

Disable cfi for AFDO collecting builders.

We disabled thinlto on AFDO collecting builders. cfi is dependent on
thinlto, so we need to disable cfi on these builders too.

BUG= chromium:828593 
TEST=run_test passes.

Change-Id: I6b02329d018e5124b105dd6d0c95f17f8d7d57d8
Reviewed-on: https://chromium-review.googlesource.com/1094560
Commit-Ready: Yunlian Jiang <yunlian@chromium.org>
Tested-by: Yunlian Jiang <yunlian@chromium.org>
Reviewed-by: Yunlian Jiang <yunlian@chromium.org>

[modify] https://crrev.com/863eebc081b86e7d830b6dfb8200be80cb27959c/config/chromeos_config.py
[modify] https://crrev.com/863eebc081b86e7d830b6dfb8200be80cb27959c/config/config_dump.json