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

infra_libs/ts_mon/common/metrics.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Classes representing individual metrics that can be sent."""
 
 import copy
 import operator
 import threading
 import time
@@ skipping 45 matching lines @@
       description (string): help string for the metric. Should be enough to
                             know what the metric is about.
     """
     self._name = name.lstrip('/')
     self._start_time = None
     fields = fields or {}
     if len(fields) > 7:
       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)
 
   @property
   def name(self):
     return self._name
 
   @property
   def start_time(self):
@@ skipping 16 matching lines @@
     Args:
       collection_pb (metrics_pb2.MetricsCollection): protocol buffer into which
         to add the current metric values.
       start_time (int): timestamp in microseconds since UNIX epoch.
       target (Target): a Target to use.
     """
 
     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)
 
     target._populate_target_pb(metric_pb)
 
   def _populate_fields(self, metric, fields):
     """Fill in the fields attribute of a metric protocol buffer.
 
     Args:
@@ skipping 339 matching lines @@
                description=None):
     super(NonCumulativeDistributionMetric, self).__init__(
         name,
         is_cumulative=False,
         bucketer=bucketer,
         fields=fields,
         description=description)
 
   def is_cumulative(self):
     return False