Remove navigate measurements since it's not used anywhere.

tools/perf/measurements/navigate.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.
-
-from telemetry.page import page_measurement
-
-class NavigateMeasurement(page_measurement.PageMeasurement):
-  """ Measures time between navigation start and the end of the navigate_steps
-
-  For pages where the 'load' event isn't a good measurement point, this
-  measurement allows a page_set to have its loading sequence listed by
-  way of navigate_steps, with a navigation_time result measured
-  by performance.now().
-  """
-  def __init__(self):
-    super(NavigateMeasurement, self).__init__()
-    self._navigate_time = None
-
-  def DidNavigateToPage(self, page, tab):
-    self._navigate_time = int(tab.EvaluateJavaScript('performance.now()'))
-
-  def MeasurePage(self, page, tab, results):
-    results.Add('navigate_time', 'ms', self._navigate_time)