Add CIPD pin reporting to swarming.

appengine/swarming/swarming_rpcs.py

Index: appengine/swarming/swarming_rpcs.py
diff --git a/appengine/swarming/swarming_rpcs.py b/appengine/swarming/swarming_rpcs.py
index 6c290eabf170b66a50fa05f919ff28f70da9a78c..2a33b0dd9fb4be9e2ffecb85041bef5dbf1085b2 100644
--- a/appengine/swarming/swarming_rpcs.py
+++ b/appengine/swarming/swarming_rpcs.py
@@ -280,6 +280,11 @@ class TaskResult(messages.Message):
   # Statistics about overhead for an isolated task. Only sent when requested.
   performance_stats = messages.MessageField(PerformanceStats, 26)
 
+  # A listing of the ACTUAL pinned CipdPackages that the task used. These can
+  # vary from the input packages if the inputs included non-identity versions
+  # (e.g. a ref like "latest").
+  cipd_pins = messages.MessageField(CipdPackage, 27, repeated=True)
+
 
 class TaskList(messages.Message):
   """Wraps a list of TaskResult."""