Apply gerrit ref if it is a Gerrit patch.

Also:
* Pass through a new property 'patch_storage' to DM/Nanobench/Coverage. This will be used by the different frameworks to figure out if it is Rietveld or Gerrit issue.
* Calculate issue and patchset for Gerrit patches similar to Rietveld.

BUG=skia:5627
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2263323002

Review-Url: https://codereview.chromium.org/2263323002
16 files changed