Dashboard - Remove pre-hook logic from alert.py.

dashboard/dashboard/update_bug_with_results.py

Index: dashboard/dashboard/update_bug_with_results.py
diff --git a/dashboard/dashboard/update_bug_with_results.py b/dashboard/dashboard/update_bug_with_results.py
index 3eb7a935ac3391595eef65b840a86e34d2f9b1e2..673dcf32e785d5351256e89d67d422d35574c21d 100644
--- a/dashboard/dashboard/update_bug_with_results.py
+++ b/dashboard/dashboard/update_bug_with_results.py
@@ -21,6 +21,7 @@ from dashboard import quick_logger
 from dashboard.common import datastore_hooks
 from dashboard.common import request_handler
 from dashboard.common import utils
+from dashboard.models import alert_group
 from dashboard.models import anomaly
 from dashboard.models import bug_data
 from dashboard.models import try_job
@@ -333,9 +334,9 @@ def _MapAnomaliesToMergeIntoBug(dest_bug_id, source_bug_id):
   query = anomaly.Anomaly.query(
       anomaly.Anomaly.bug_id == int(source_bug_id))
   anomalies = query.fetch()
-  for anomaly_entity in anomalies:
-    anomaly_entity.bug_id = int(dest_bug_id)
-  ndb.put_multi(anomalies)
+
+  alert_group.ModifyAlertsAndAssociatedGroups(
+      anomalies, bug_id=int(dest_bug_id))
 
 
 def _GetCommitHashCacheKey(results_data):