Generalize patch_project to patch root conversion.

recipe_modules/bot_update/api.py

Index: recipe_modules/bot_update/api.py
diff --git a/recipe_modules/bot_update/api.py b/recipe_modules/bot_update/api.py
index 31a27335c82c2d67528b6906cce51b748dfd6c98..a8d7a7b43b52e6b6744d022d7ce4fc7b55aba293 100644
--- a/recipe_modules/bot_update/api.py
+++ b/recipe_modules/bot_update/api.py
@@ -85,6 +85,12 @@ class BotUpdateApi(recipe_api.RecipeApi):
     # Construct our bot_update command.  This basically be inclusive of
     # everything required for bot_update to know:
     root = patch_root
+    if root == 'TODO(TANDRII): REMOVE THIS TRANSITION TO patch_projects':
+      assert patch_project_roots is None
+      root = self.m.gclient.calculate_patch_root(
+          self.m.properties.get('patch_project'), cfg)
+      # TODO(tandrii): get rid the condition below after transition.
+
     if root is None:
       root = cfg.solutions[0].name
       additional = self.m.rietveld.calculate_issue_root(patch_project_roots)