Add CsvOutputFormatter to Telemetry.

telemetry/telemetry/internal/results/csv_output_formatter.py

Index: telemetry/telemetry/internal/results/csv_output_formatter.py
diff --git a/telemetry/telemetry/internal/results/csv_output_formatter.py b/telemetry/telemetry/internal/results/csv_output_formatter.py
new file mode 100644
index 0000000000000000000000000000000000000000..d9dc885e86c13c5aa17a8df3546cfd0da041c21a
--- /dev/null
+++ b/telemetry/telemetry/internal/results/csv_output_formatter.py
@@ -0,0 +1,56 @@
+# 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 collections
+import csv
+import json
+import os
+import tempfile
+
+from telemetry.internal.results import output_formatter
+from tracing.value import histograms_to_csv
+
+
+def _ReadCsv(text):
+  dicts = []
+  header = None
+  for row in csv.reader(text.split('\n')):
+    if header is None:
+      header = row
+    elif row:
+      dicts.append(collections.OrderedDict(zip(header, row)))
+  return dicts
+
+
+def _WriteCsv(dicts, fileobj):
+  header = []
+  for d in dicts:
+    for k in d.iterkeys():
+      if k not in header:
+        header.append(k)
+  rows = [header]
+  for d in dicts:
+    rows.append([d.get(k, '') for k in header])
+  csv.writer(fileobj).writerows(rows)
+
+
+class CsvOutputFormatter(output_formatter.OutputFormatter):
+  def __init__(self, output_stream, reset_results=False):
+    super(CsvOutputFormatter, self).__init__(output_stream)
+    self._reset_results = reset_results
+
+  def Format(self, page_test_results):
+    histograms = page_test_results.AsHistogramDicts()
+    file_descriptor, json_path = tempfile.mkstemp()
+    os.close(file_descriptor)
+    json.dump(histograms, file(json_path, 'w'))
+    vinn_result = histograms_to_csv.HistogramsToCsv(json_path)
+    dicts = _ReadCsv(vinn_result.stdout)
+
+    self._output_stream.seek(0)
+    if not self._reset_results:
+      dicts += _ReadCsv(self._output_stream.read())
+      self._output_stream.seek(0)
+    _WriteCsv(dicts, self._output_stream)
+    self._output_stream.truncate()