[Findit] Refactoring trigger swarming task pipelines

appengine/findit/model/wf_swarming_task.py

Index: appengine/findit/model/wf_swarming_task.py
diff --git a/appengine/findit/model/wf_swarming_task.py b/appengine/findit/model/wf_swarming_task.py
index 066cd662ee287ade6833f16b94e3b225b6c4ea70..9c473f818d5cefb61d52ff3dd2d56c00de402cf9 100644
--- a/appengine/findit/model/wf_swarming_task.py
+++ b/appengine/findit/model/wf_swarming_task.py
@@ -45,6 +45,10 @@ class WfSwarmingTask(BaseBuildModel, BaseSwarmingTask):
   def reliable_tests(self):
     return self.classified_tests.get('reliable_tests', [])
 
+  @ndb.ComputedProperty
+  def step_name(self):
+    return self.key.pairs()[1][1]
+
   @staticmethod
   def _CreateKey(
       master_name, builder_name, build_number, step_name):  # pragma: no cover