Set up the infrastructure for Extension event metrics.

tools/metrics/histograms/update_extension_histograms.py

+# Copyright 2013 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.
+
+"""Updates ExtensionEvents and ExtensionFunctions enum in histograms.xml file
+with values read from extension_event_histogram_value.h and
+extension_function_histogram_value.h.
+
+If the file was pretty-printed, the updated version is pretty-printed too.
+"""
+
+import os
+import sys
+
+from update_histogram_enum import UpdateHistogramEnum
+
+if __name__ == '__main__':
+  if len(sys.argv) > 1:
+    print >>sys.stderr, 'No arguments expected!'
+    sys.stderr.write(__doc__)
+    sys.exit(1)
+
+  histograms = (
+    ('ExtensionEvents',

[not at google - send to devlin, 2015/06/22 23:42:11]

This is just update_extension_functions.py moved, then updated to also modify
the events.

+     'extensions/browser/extension_event_histogram_value.h'),
+    ('ExtensionFunctions',
+     'extensions/browser/extension_function_histogram_value.h'))
+  for enum_name, source_header in histograms:
+    UpdateHistogramEnum(histogram_enum_name=enum_name,
+                        source_enum_path=source_header,
+                        start_marker='^enum HistogramValue {',
+                        end_marker='^ENUM_BOUNDARY')