Add apply_gerrit_ref to bot_update api

recipe_modules/tryserver/api.py

Index: recipe_modules/tryserver/api.py
diff --git a/recipe_modules/tryserver/api.py b/recipe_modules/tryserver/api.py
index f18c2b5d93227ffe0cf4c351de2dcf3b64dbfdb3..f4a09a37d461c1f527de5d76633f90b0a94b2681 100644
--- a/recipe_modules/tryserver/api.py
+++ b/recipe_modules/tryserver/api.py
@@ -5,11 +5,15 @@
 import collections
 import contextlib
 import hashlib
+import os
+import sys
+import uuid
 
 from recipe_engine import recipe_api
 
 
 PATCH_STORAGE_RIETVELD = 'rietveld'
+PATCH_STORAGE_GERRIT = 'gerrit'
 PATCH_STORAGE_GIT = 'git'
 PATCH_STORAGE_SVN = 'svn'
 
@@ -136,11 +140,17 @@ class TryserverApi(recipe_api.RecipeApi):
         None, 'oauth2' (see also api.rietveld.apply_issue.)
     """
     storage = self.determine_patch_storage()
-
     if storage == PATCH_STORAGE_RIETVELD:
       return self.m.rietveld.apply_issue(
           self.m.rietveld.calculate_issue_root(),
           authentication=authentication)
+    elif storage == PATCH_STORAGE_GERRIT:

[tandrii(chromium), 2016/08/19 14:00:04]

Hm, can you move this condition instead to skia recipe just to get going?

[rmistry, 2016/08/19 14:36:08]

That makes sense. Will do.

+      patch_project = (self.m.properties.get('patch_project') or
+                       self.m.properties.get('project'))
+      return self.m.bot_update.apply_gerrit_ref(
+          gerrit_repo=self.m.properties.get('repository') or 'origin',
+          gerrit_ref=self.m.properties.get('event.patchSet.ref'),
+          root=str(self.m.path['slave_build'].join(patch_project)))
     elif storage == PATCH_STORAGE_SVN:
       return self.apply_from_svn(cwd)
     elif storage == PATCH_STORAGE_GIT: