Create a UKM descriptions XML file

tools/metrics/ukm/pretty_print.py

Index: tools/metrics/ukm/pretty_print.py
diff --git a/tools/metrics/ukm/pretty_print.py b/tools/metrics/ukm/pretty_print.py
new file mode 100755
index 0000000000000000000000000000000000000000..8398ed3101faf3a71446cefd5695cf083a21a544
--- /dev/null
+++ b/tools/metrics/ukm/pretty_print.py
@@ -0,0 +1,21 @@
+#!/usr/bin/env python
+# Copyright 2017 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.
+
+import os
+import sys
+
+import model
+sys.path.append(os.path.join(os.path.dirname(__file__), '..', 'common'))
+import presubmit_util
+
+
+
+def main(argv):
+  presubmit_util.DoPresubmitMain(argv, 'ukm.xml', 'ukm.old.xml',
+                                 'pretty_print.py', model.UpdateXML)
+
+
+if '__main__' == __name__:
+  sys.exit(main(sys.argv))