[Telemetry] Fix --cold-load-percent.

tools/perf/measurements/page_cycler_unittest.py

 # Copyright 2013 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 unittest
 
 from measurements import page_cycler
 from telemetry.core import browser_options
 from telemetry.page import page_measurement_results
 from telemetry.unittest import simple_mock
 
@@ skipping 20 matching lines @@
 
 # Used to mock loading a page.
 class FakePage(object):
   def __init__(self, url):
     self.url = url
 
 # Used to mock a browser tab.
 class FakeTab(object):
   def __init__(self):
     self.clear_cache_calls = 0
-  def ClearCache(self):
+  def ClearCache(self, force=False):
+    assert force
     self.clear_cache_calls += 1
   def EvaluateJavaScript(self, _):
     return 1
   def WaitForJavaScriptExpression(self, _, __):
     pass
 
 class PageCyclerUnitTest(unittest.TestCase):
 
   # TODO(tonyg): Remove this backfill when we can assume python 2.7 everywhere.
   def assertIn(self, first, second, _=None):
@@ skipping 98 matching lines @@
         values = results.page_specific_values_for_current_page
         results.DidMeasurePage()
 
         self.assertEqual(1, len(values))
         self.assertEqual(values[0].page, page)
 
         chart_name = 'cold_times' if i == 0 else 'warm_times'
         self.assertEqual(values[0].name, '%s.page_load_time' % chart_name)
 
         cycler.DidNavigateToPage(page, tab)