Telemetry: Fix several small problems in the profile creator.

tools/perf/profile_creators/fast_navigation_profile_extender_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 unittest
 
 from profile_creators.fast_navigation_profile_extender import (
     FastNavigationProfileExtender)
 from telemetry.core import util
 
 util.AddDirToPythonPath(util.GetTelemetryDir(), 'third_party', 'mock')
 import mock
 
 
 class FakeTab(object):
   pass
 
 
+class FakeTabList(object):
+  def __init__(self):
+    self._tabs = []
+
+  def New(self):
+    tab = FakeTab()
+    self._tabs.append(tab)
+    return tab
+
+  def __len__(self):
+    return len(self._tabs)
+
+
 class FakeBrowser(object):
-  def __init__(self, tab_count):
-    self.tabs = []
-    for _ in range(tab_count):
-      self.tabs.append(FakeTab())
+  def __init__(self):
+    self.tabs = FakeTabList()
 
 
 # Testing private method.
 # pylint: disable=protected-access
 class FastNavigationProfileExtenderTest(unittest.TestCase):
   def testPerformNavigations(self):
     maximum_batch_size = 15
     extender = FastNavigationProfileExtender(maximum_batch_size)
 
     navigation_urls = []
     for i in range(extender._NUM_TABS):
       navigation_urls.append('http://test%s.com' % i)
     batch_size = 5
     navigation_urls_batch = navigation_urls[3:3 + batch_size]
 
     extender.GetUrlIterator = mock.MagicMock(
         return_value=iter(navigation_urls_batch))
     extender.ShouldExitAfterBatchNavigation = mock.MagicMock(return_value=True)
     extender._WaitForQueuedTabsToLoad = mock.MagicMock()
 
-    extender._browser = FakeBrowser(extender._NUM_TABS)
+    extender._browser = FakeBrowser()
     extender._BatchNavigateTabs = mock.MagicMock()
 
     # Set up a callback to record the tabs and urls in each navigation.
     callback_tabs_batch = []
     callback_urls_batch = []
     def SideEffect(*args, **_):
       batch = args[0]
       for tab, url in batch:
         callback_tabs_batch.append(tab)
         callback_urls_batch.append(url)
     extender._BatchNavigateTabs.side_effect = SideEffect
 
     # Perform the navigations.
     extender._PerformNavigations()
 
     # Each url in the batch should have been navigated to exactly once.
     self.assertEqual(set(callback_urls_batch), set(navigation_urls_batch))
 
     # The other urls should not have been navigated to.
     navigation_urls_remaining = (set(navigation_urls) -
         set(navigation_urls_batch))
     self.assertFalse(navigation_urls_remaining & set(callback_urls_batch))
 
     # The first couple of tabs should have been navigated once. The remaining
     # tabs should not have been navigated.
     for i in range(len(extender._browser.tabs)):
-      tab = extender._browser.tabs[i]
+      tab = extender._browser.tabs._tabs[i]
 
       if i < batch_size:
         expected_tab_navigation_count = 1
       else:
         expected_tab_navigation_count = 0
 
       count = callback_tabs_batch.count(tab)
       self.assertEqual(count, expected_tab_navigation_count)