[Telemetry] Make "discard_first_result" apply to user_stories too.

tools/telemetry/telemetry/results/page_test_results.py

Index: tools/telemetry/telemetry/results/page_test_results.py
diff --git a/tools/telemetry/telemetry/results/page_test_results.py b/tools/telemetry/telemetry/results/page_test_results.py
index 497a3aea9d0b5cce7fb7157abbbd1e6cad7b7af9..38b62e448bfdfdc43a322f4df8f9e66d7aa0b540 100644
--- a/tools/telemetry/telemetry/results/page_test_results.py
+++ b/tools/telemetry/telemetry/results/page_test_results.py
@@ -23,7 +23,7 @@ from telemetry.value import trace
 class PageTestResults(object):
   def __init__(self, output_stream=None, output_formatters=None,
                progress_reporter=None, trace_tag='', output_dir=None,
-               value_can_be_added_predicate=lambda v: True):
+               value_can_be_added_predicate=lambda v, is_first: True):
     """
     Args:
       output_stream: The output stream to use to write test results.
@@ -36,9 +36,10 @@ class PageTestResults(object):
           used for buildbot.
       output_dir: A string specified the directory where to store the test
           artifacts, e.g: trace, videos,...
-      value_can_be_added_predicate: A function that takes an value.Value
-          instance as input. It returns True if the value can be added to the
-          test results and False otherwise.
+      value_can_be_added_predicate: A function that takes two arguments:
+          a value.Value instance and a boolean (True when the value is part
+          of the first result for the user story). It returns True if the value
+          can be added to the test results and False otherwise.
     """
     # TODO(chrishenry): Figure out if trace_tag is still necessary.
 
@@ -55,6 +56,7 @@ class PageTestResults(object):
 
     self._current_page_run = None
     self._all_page_runs = []
+    self._all_user_stories = set()
     self._representative_value_for_each_value_name = {}
     self._all_summary_values = []
     self._serialized_trace_file_ids_to_paths = {}
@@ -153,23 +155,23 @@ class PageTestResults(object):
     self._current_page_run = user_story_run.UserStoryRun(page)
     self._progress_reporter.WillRunPage(self)
 
-  def DidRunPage(self, page, discard_run=False):  # pylint: disable=W0613
+  def DidRunPage(self, page):  # pylint: disable=W0613
     """
     Args:
       page: The current page under test.
-      discard_run: Whether to discard the entire run and all of its
-          associated results.
     """
     assert self._current_page_run, 'Did not call WillRunPage.'
     self._progress_reporter.DidRunPage(self)
-    if not discard_run:
-      self._all_page_runs.append(self._current_page_run)
+    self._all_page_runs.append(self._current_page_run)
+    self._all_user_stories.add(self._current_page_run.user_story)
     self._current_page_run = None
 
   def AddValue(self, value):
     assert self._current_page_run, 'Not currently running test.'
     self._ValidateValue(value)
-    if not self._value_can_be_added_predicate(value):
+    is_first_result = (
+      self._current_page_run.user_story not in self._all_user_stories)
+    if not self._value_can_be_added_predicate(value, is_first_result):
       return
     # TODO(eakuefner/chrishenry): Add only one skip per pagerun assert here
     self._current_page_run.AddValue(value)