PRESUBMIT: rename trybots from gn to gyp.

PRESUBMIT: rename trybots from gn to gyp.

After switching the default bots from GYP to GN,
we now only have a few GYP bots left, so rename the trybots
accordingly

BUG=chromium:652188
TBR=fbarchard@chromium.org

Committed: https://chromium.googlesource.com/libyuv/libyuv/+/fcbb30f593021a4ff751c4c32d2c417a47c554dd

[kjellander_chromium, 2016-10-17 13:09:59]

Description was changed from

==========
PRESUBMIT: rename trybots from gn to gyp.

After switching the default bots from GYP to GN,
we now only have a few GYP bots left, so rename the trybots
accordingly

BUG=chromium:652188
TBR=fbarchard@chromium.org
==========

to

==========
PRESUBMIT: rename trybots from gn to gyp.

After switching the default bots from GYP to GN,
we now only have a few GYP bots left, so rename the trybots
accordingly

BUG=chromium:652188
TBR=fbarchard@chromium.org

Committed:
https://chromium.googlesource.com/libyuv/libyuv/+/fcbb30f593021a4ff751c4c32d2...
==========

[kjellander_chromium, 2016-10-17 13:10:01]

Committed patchset #1 (id:1) manually as
fcbb30f593021a4ff751c4c32d2c417a47c554dd (presubmit successful).

[fbarchard1, 2016-10-17 17:00:50]

fbarchard@google.com changed reviewers:
+ fbarchard@google.com

[fbarchard1, 2016-10-17 17:00:50]

looks like this breaks the bots.  will need a followup to fix

[kjellander_chromium, 2016-10-18 06:18:12]

On 2016/10/17 17:00:50, fbarchard1 wrote:
> looks like this breaks the bots.  will need a followup to fix

I don't think this particular change is breaking the bots, but there's been a
few problems with old build artifacts from GYP that causes an error when running
GN. I was trying to clear them out with landmines but it doesn't seem to be
working as intended yet.