Fix navigation to unittest files

tools/telemetry/telemetry/unittest/tab_test_case.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 unittest
 
 from telemetry.core import browser_finder
+from telemetry.unittest import navigate_test
 from telemetry.unittest import options_for_unittests
 
 class TabTestCase(unittest.TestCase):
   def __init__(self, *args):
     self._extra_browser_args = []
+    self.test_file_path = None
     super(TabTestCase, self).__init__(*args)
 
   def setUp(self):
     self._browser = None
     self._tab = None
     options = options_for_unittests.GetCopy()
 
     self.CustomizeBrowserOptions(options)
 
     if self._extra_browser_args:
@@ skipping 15 matching lines @@
 
   def tearDown(self):
     if self._tab:
       self._tab.Disconnect()
     if self._browser:
       self._browser.Close()
 
   def CustomizeBrowserOptions(self, options):
     """Override to add test-specific options to the BrowserOptions object"""
     pass
+
+  def Navigate(self, filename, script_to_evaluate_on_commit=None):
+    """Navigates |tab| to |filename| in the unittest data directory.
+
+    Also sets up http server to point to the unittest data directory.
+    """
+    self.test_file_path = navigate_test.NavigateToTestFile(
+        self._tab, filename, script_to_evaluate_on_commit)