Update metrics.proto, and set metric descriptions in MetricsData messages

infra_libs/ts_mon/common/metrics.py

Index: infra_libs/ts_mon/common/metrics.py
diff --git a/infra_libs/ts_mon/common/metrics.py b/infra_libs/ts_mon/common/metrics.py
index e68e7408b1969761b46934af5fd846e91f06a647..bfaf7f223e56a011057fa5c7cdd94118e6de6e1a 100644
--- a/infra_libs/ts_mon/common/metrics.py
+++ b/infra_libs/ts_mon/common/metrics.py
@@ -63,8 +63,6 @@ class Metric(object):
       raise errors.MonitoringTooManyFieldsError(self._name, fields)
     self._fields = fields
     self._normalized_fields = self._normalize_fields(self._fields)
-    # pgervais: Yes, description is unused. Waiting for the rest of the pipeline
-    # to support it.
     self._description = description
 
     interface.register(self)
@@ -101,6 +99,8 @@ class Metric(object):
     metric_pb = collection_pb.data.add()
     metric_pb.metric_name_prefix = '/chrome/infra/'
     metric_pb.name = self._name
+    if self._description is not None:
+      metric_pb.description = self._description
 
     self._populate_value(metric_pb, value, start_time)
     self._populate_fields(metric_pb, fields)