Reason for revert:
Instead of trying to run the presubmit for try jobs and at every commit, let's do it only for try jobs, which worked fine without this CL.
Original issue's description:
> Presubmit recipe: call presubmit_support.py directly
>
> For some reason, presubmit_support.py can't find PRESUBMIT.py
> unless it has a diff. Calling this script directly allows us
> to specify a fake upstream to force it to find a diff and
> therefore be able to find PRESUBMIT.py.
>
> BUG=skia:5823
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2398653002
>
> Committed: https://skia.googlesource.com/skia/+/c1c7c21fdd2793b2c03b8ffc06461a00c4241a18TBR=rmistry@google.com,borenet@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=skia:5823
Review-Url: https://codereview.chromium.org/2414133003
For some reason, presubmit_support.py can't find PRESUBMIT.py
unless it has a diff. Calling this script directly allows us
to specify a fake upstream to force it to find a diff and
therefore be able to find PRESUBMIT.py.
BUG=skia:5823
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2398653002
Review-Url: https://codereview.chromium.org/2398653002
