[telemetry] Move Results options out of PageTest/Measurement into their own module.

tools/telemetry/telemetry/page/csv_page_measurement_results.py

 # Copyright (c) 2012 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 csv
 
 from telemetry.page import page_measurement_results
 
 class CsvPageMeasurementResults(
     page_measurement_results.PageMeasurementResults):
-  def __init__(self, output_stream=None, output_after_every_page=None):
+  def __init__(self, output_stream, output_after_every_page=None):
     super(CsvPageMeasurementResults, self).__init__()
-    if output_stream:
-      self._results_writer = csv.writer(output_stream)
+    self._results_writer = csv.writer(output_stream)
     self._did_output_header = False
     self._header_names_written_to_writer = None
     self._output_after_every_page = output_after_every_page
 
   def DidMeasurePage(self):
     assert self.values_for_current_page, 'Failed to call WillMeasurePage'
 
     if (not self.values_for_current_page.values or
         not self._output_after_every_page):
       # Do not output if no results were added on this page or if output flag
@@ skipping 56 matching lines @@
 
   def _OutputValuesForPage(self, page_values):
     row = [page_values.page.display_url]
     for measurement_name in self._header_names_written_to_writer:
       value = page_values.FindValueByMeasurementName(measurement_name)
       if value:
         row.append('%s' % value.output_value)
       else:
         row.append('-')
     self._results_writer.writerow(row)