Added git-hash-metrics builder and recipe

masters/master.chromium.infra.cron/slaves.cfg

 # -*- python -*-
 # ex: set syntax=python:
 
 # 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.
 
 slaves = [
   {
     'master': 'InfraCron',
@@ skipping 110 matching lines @@
   {
     'master': 'InfraCron',
     'builder': ['Chromium Linux Codesearch'],
     'hostname': 'slave14-c1',
   },
   {
     'master': 'InfraCron',
     'builder': ['ChromiumOS Codesearch'],
     'hostname': 'slave15-c1',
   },
+  {
+    'master': 'InfraCron',
+    'builder': ['git-hash-metrics'],
+    'hostname': 'slave71-c1',
+  },
 ]