Add Multi-tab System Health Story

tools/perf/measurements/tab_switching_unittest.py

 # Copyright 2015 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 contextlib
 from telemetry.internal.results import page_test_results
 from telemetry.testing import page_test_test_case
 
 from measurements import tab_switching
 
@@ skipping 47 matching lines @@
     browser = BrowserForTest()
     tab_0 = self.MakeTabForTest()
     browser.AddTab(tab_0)
     tab_1 = self.MakeTabForTest()
     browser.AddTab(tab_1)
 
     # Mock histogram result to test _IsDone really works.
     expected_histogram = [
         # To get first_histogram for last tab (tab_1).
         '{"count": 0, "buckets": []}',
-        # First _IsDone check for tab_0. Retry.
-        '{"count": 0, "buckets": []}',
-        # Second _IsDone check for tab_0. Retry.
-        '{"count": 0, "buckets": []}',
-        # Third _IsDone check for tab_0. Pass.
-        '{"count": 1, "buckets": [{"low": 1, "high": 2, "count": 1}]}',
-        # To get prev_histogram. End of tab_0 loop.
-        '{"count": 1, "buckets": [{"low": 1, "high": 2, "count": 1}]}',
-        # First _IsDone check for tab_1. Retry.
-        '{"count": 1, "buckets": [{"low": 1, "high": 2, "count": 1}]}',
-        # Second _IsDone check for tab_1. Pass.
-        '{"count": 2, "buckets": [{"low": 1, "high": 2, "count": 1},'
-        '{"low": 2, "high": 3, "count": 1}]}',
         # To get prev_histogram. End of tab_1 loop.
         '{"count": 2, "buckets": [{"low": 1, "high": 2, "count": 1},'
         '{"low": 2, "high": 3, "count": 1}]}',
         ]
     mock_get_histogram = mock.MagicMock(side_effect=expected_histogram)
 
     with contextlib.nested(
         mock.patch('telemetry.value.histogram_util.GetHistogram',
                    mock_get_histogram),
         mock.patch('metrics.keychain_metric.KeychainMetric')):
+      measure.DidNavigateToPage(story_set.stories[0], browser.tabs[-1])
       measure.ValidateAndMeasurePage(story_set.stories[0], browser.tabs[-1],
                                      page_test_results.PageTestResults())
       self.assertEqual(len(expected_histogram),
                        len(mock_get_histogram.mock_calls))
       expected_calls = [mock.call(mock.ANY, mock.ANY, t) for t in
-                        [tab_1] + [tab_0] * 4 + [tab_1] * 3]
+                        [tab_1] + [tab_1]]
       self.assertEqual(expected_calls, mock_get_histogram.mock_calls)