Remove dwm function because it is going away in windows 8.1

tools/telemetry/telemetry/core/tab_unittest.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 logging
 import os
+import time
 
 from telemetry.core import util
 from telemetry.core import exceptions
 from telemetry.unittest import tab_test_case
 
 
 def _IsDocumentVisible(tab):
   state = tab.EvaluateJavaScript('document.webkitVisibilityState')
   # TODO(dtu): Remove when crbug.com/166243 is fixed.
   tab.Disconnect()
@@ skipping 48 matching lines @@
       return
 
     unittest_data_dir = os.path.join(os.path.dirname(__file__),
                                      '..', '..', 'unittest_data')
     self._browser.SetHTTPServerDirectories(unittest_data_dir)
     self._tab.Navigate(
       self._browser.http_server.UrlOf('green_rect.html'))
     self._tab.WaitForDocumentReadyStateToBeComplete()
     pixel_ratio = self._tab.EvaluateJavaScript('window.devicePixelRatio || 1')
 
+    # TODO(bajones): Sleep for a bit to counter BUG 260878.
+    time.sleep(0.5)
     screenshot = self._tab.Screenshot(5)
     assert screenshot
     screenshot.GetPixelColor(0 * pixel_ratio, 0 * pixel_ratio).AssertIsRGB(
         0, 255, 0, tolerance=2)
     screenshot.GetPixelColor(31 * pixel_ratio, 31 * pixel_ratio).AssertIsRGB(
         0, 255, 0, tolerance=2)
     screenshot.GetPixelColor(32 * pixel_ratio, 32 * pixel_ratio).AssertIsRGB(
         255, 255, 255, tolerance=2)