Convert chart-json to Histograms.

tracing/bin/chartjson2histograms

+#!/usr/bin/env python
+# Copyright 2016 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 argparse
+import os
+import sys
+
+tracing_path = os.path.abspath(os.path.join(os.path.dirname(__file__),
+                               '..'))
+sys.path.append(tracing_path)
+from tracing.value import convert_chart_json
+
+
+def Main(argv):
+  parser = argparse.ArgumentParser(
+      description='Compare samples.')
+  parser.add_argument('chart_json', type=str, help='(input)')
+  parser.add_argument('histogram_json', type=str, help='(input/output)')
+  args = parser.parse_args(argv[1:])
+
+  vinn_result = convert_chart_json.ConvertChartJson(args.chart_json)
+
+  if vinn_result.returncode == 0:
+    histograms = json.loads(vinn_result.stdout)
+    if os.path.exists(args.histogram_json):
+      histograms.extend(json.load(file(args.histogram_json, 'r')))

[nednguyen, 2016/11/03 21:10:24]

This could be confusing to people that if they run the command twice, they get
the histograms duplicated.

Is there any reason why you support appending? If not, I would just always write
to the file

[benjhayden, 2016/11/09 23:48:55]

valueset2html reads existing results from the output file.

+    json.dump(histograms, file(args.histogram_json, 'w'))
+
+  return vinn_result.returncode
+
+if __name__ == '__main__':
+  sys.exit(Main(sys.argv))