The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/2ee78eeb401bdf66dd94b0a185e210ace72dee64

commit 2ee78eeb401bdf66dd94b0a185e210ace72dee64
Author: Caroline Tice <cmtice@google.com>
Date: Sat Mar 04 08:43:19 2017

[waterfall] Remove x86 toolchain waterfall builders

The x86 boards have reached their end-of-life, so we no longer need
to monitor them on our waterfalls.  This CL removes the x86 toolchain
builders from the waterfall.

BUG= chromium:698434 
TEST=Ran run_tests with no errors.

Change-Id: I4bcb0083d001115cc95adaf4e583366966075080
Reviewed-on: https://chromium-review.googlesource.com/449880
Commit-Ready: Caroline Tice <cmtice@chromium.org>
Tested-by: Caroline Tice <cmtice@chromium.org>
Reviewed-by: Caroline Tice <cmtice@chromium.org>

[modify] https://crrev.com/2ee78eeb401bdf66dd94b0a185e210ace72dee64/cbuildbot/config_dump.json
[modify] https://crrev.com/2ee78eeb401bdf66dd94b0a185e210ace72dee64/cbuildbot/waterfall_layout_dump.txt
[modify] https://crrev.com/2ee78eeb401bdf66dd94b0a185e210ace72dee64/cbuildbot/chromeos_config.py

What about x86-generic, will we keep this?

we are only modifying the "toolchain row" of builders. 
The other uses of x86 remain in the waterfall remain until build team decides to remove them.

I'd like to be able to build x86-generic images for a while, even if they are not officially supported anymore. Ideally this x86-generic toolchain is the last one Chrome OS used, and not something reverted to upstream.

we are not changing the toolchain used to build x86 images. They will continue building  with the version of GCC (4.9.2) that we are using currently.
With this change we are stoping the testing of new compilers for x86 boards.

Makes sense.