Apply gerrit ref if it is a Gerrit patch

infra/bots/recipes/swarm_compile.py

Index: infra/bots/recipes/swarm_compile.py
diff --git a/infra/bots/recipes/swarm_compile.py b/infra/bots/recipes/swarm_compile.py
index cdf4739f443a82cee3681a6433c50c723e72f2d7..5ca28edfe5c8179b34b1f50cb8c5adf481d6867b 100644
--- a/infra/bots/recipes/swarm_compile.py
+++ b/infra/bots/recipes/swarm_compile.py
@@ -107,7 +107,7 @@ def get_gyp_defines(builder_dict):
     werr = False
   elif 'Fast' in builder_dict.get('extra_config', ''):
     # See https://bugs.chromium.org/p/skia/issues/detail?id=5257
-    werr = False  
+    werr = False
   else:
     werr = True
   gyp_defs['skia_warnings_as_errors'] = str(int(werr))  # True/False -> '1'/'0'
@@ -309,3 +309,23 @@ def GenTests(api):
       ) +
       api.platform('win', 64)
   )
+
+  gerrit_kwargs = {
+    'patch_storage': 'gerrit',
+    'repository': 'skia',
+    'event.patchSet.ref': 'refs/changes/00/2100/2',
+    'event.change.number': '2100',
+  }
+  yield (
+      api.test('recipe_with_gerrit_patch') +
+      api.properties(
+          buildername=buildername + '-Trybot',
+          mastername=mastername,
+          slavename=slavename,
+          buildnumber=5,
+          path_config='kitchen',
+          swarm_out_dir='[SWARM_OUT_DIR]',
+          revision='abc123',
+          **gerrit_kwargs) +
+      api.platform('win', 64)
+  )