Script to populate the XML for the CSS property UseCounter.

tools/metrics/histograms/update_use_counter_css.py

Index: tools/metrics/histograms/update_use_counter_css.py
diff --git a/tools/metrics/histograms/update_use_counter_css.py b/tools/metrics/histograms/update_use_counter_css.py
new file mode 100644
index 0000000000000000000000000000000000000000..d4e5beaed251fdc2f57802893b6cc3e1a8b3cb99
--- /dev/null
+++ b/tools/metrics/histograms/update_use_counter_css.py
@@ -0,0 +1,66 @@
+#!/usr/bin/env python
+# Copyright 2014 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.
+
+"""Scans the Chromium source of UseCounter, formats the Feature enum for
+histograms.xml and merges it. This script can also generate a python code
+snippet to put in uma.py of Chromium Dashboard. Make sure that you review the
+output for correctness.
+"""
+
+import optparse
+import os
+import re
+import sys
+
+sys.path.append(os.path.join(os.path.dirname(__file__), '..', 'common'))
+from update_histogram_enum import ReadHistogramValues
+from update_histogram_enum import UpdateHistogramFromDict
+from update_use_counter_feature_enum import print_enum_for_dashboard
+
+
+USE_COUNTER_CPP_PATH = \
+    '../../../third_party/WebKit/Source/core/frame/UseCounter.cpp'
+
+
+def enum_to_css_property(enum_name):
+  """Converts a camel cased enum name to the lower case CSS property."""
+  return re.sub(r'([a-zA-Z])([A-Z])', r'\1-\2', enum_name).lower()

[Ilya Sherman, 2014/05/13 03:11:33]

Hmm, why does the first captured group have uppercase letters?

[Mike Lawther (Google), 2014/05/20 07:45:03]

Good question! This was to deal with the property 'z-index', which gets
camelCased as ZIndex. This was the only property for which my original regex (I
think I just had r'([a-z])([A-Z])') didn't work.

[Ilya Sherman, 2014/05/20 14:13:17]

Hmm, how odd.  Could you please add a comment explaining this?

[Mike Lawther (Google), 2014/05/21 07:30:41]

Done.

+
+
+def read_css_properties(filename):

[Ilya Sherman, 2014/05/13 03:11:33]

nit: I think function names are supposed to be written in CamelCase.

[Mike Lawther (Google), 2014/05/20 07:45:03]

Oh OK. I'd seen others in lower case (eg in update_use_counter_feature_enum.py),
and reverse engineered the reasoning that lower case was intended to be
'private' and CamelCase was intended to be used externally.

But happy to update all these to CamelCase. I'll change
update_use_counter_features.py as well.

+  # Read the file as a list of lines
+  with open(filename) as f:
+    content = f.readlines()
+
+  # Looking for a line like "case CSSPropertyGrid: return 453;"
+  bucket_finder = re.compile(r'.*CSSProperty(.*):\s*return\s*([0-9]+).*')

[Ilya Sherman, 2014/05/13 03:11:33]

nit: Could you write this as a multi-line regex, so that it's easier to read?

[Ilya Sherman, 2014/05/13 03:11:33]

nit: Do you really need the leading and trailing .*'s?

[Ilya Sherman, 2014/05/13 03:11:33]

Optional nit: I'd name this something like PROPERTY_PATTERN or BUCKET_PATTERN.

[Mike Lawther (Google), 2014/05/20 07:45:03]

Did you mean break the regex string itself out and name it? Or the compiled
regex?

[Mike Lawther (Google), 2014/05/20 07:45:03]

As in use re.MULTILINE so I can use ^ and $? Now that I've removed the leading
and trailing .*'s, is it easier to read? I'm only checking a single line of text
at a time.

[Mike Lawther (Google), 2014/05/20 07:45:03]

No. Removed. I had them there because I was using match instead of search down
below, and I had it in my head that I was searching from the beginning of the
string.

[Ilya Sherman, 2014/05/20 14:13:17]

I meant the compiled regex.

[Ilya Sherman, 2014/05/20 14:13:17]

I meant using verbose mode: https://docs.python.org/2/library/re.html#re.VERBOSE

[Mike Lawther (Google), 2014/05/21 07:30:41]

Done. I called it 'ENUM_REGEX', as that's what it's searching for.

[Mike Lawther (Google), 2014/05/21 07:30:41]

Gotcha. Done.

+
+  bucket_dict = {}

[Ilya Sherman, 2014/05/13 03:11:33]

Optional nit: I'd name this "properties"

[Mike Lawther (Google), 2014/05/20 07:45:03]

Agreed. I also changed some of the other names in here to remove 'bucket'. wdyt?

[Ilya Sherman, 2014/05/20 14:13:17]

LG, thanks :)

+  for line in content:
+    bucket_match = bucket_finder.match(line)
+    if bucket_match:
+      enum_name = bucket_match.group(1)

[Ilya Sherman, 2014/05/13 03:11:33]

Optional nit: I'd name this "property"

[Mike Lawther (Google), 2014/05/20 07:45:03]

I've left this as 'enum_name', because later down this gets passed into
'enum_to_css_property' to be turned into a property name. Does that still sound
OK?

[Ilya Sherman, 2014/05/20 14:13:17]

Ok.

+      bucket = int(bucket_match.group(2))
+      bucket_dict[bucket] = enum_to_css_property(enum_name)
+
+  return bucket_dict
+
+
+if __name__ == '__main__':
+  parser = optparse.OptionParser()
+  parser.add_option('--for-dashboard', action='store_true', dest='dashboard',
+                    default=False,
+                    help='Print enum definition formatted for use in uma.py of '
+                    'Chromium dashboard developed at '
+                    'https://github.com/GoogleChrome/chromium-dashboard')
+  options, args = parser.parse_args()
+
+  if options.dashboard:
+    enum_dict = read_css_properties(USE_COUNTER_CPP_PATH)
+    print_enum_for_dashboard(enum_dict)
+  else:
+    UpdateHistogramFromDict(
+        'MappedCSSProperties', read_css_properties(USE_COUNTER_CPP_PATH),
+        USE_COUNTER_CPP_PATH)