Telemetry: document.documentElement.scrollTop/Left is zero

tools/telemetry/telemetry/page/actions/scroll_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 os
 
 from telemetry.core import util
 from telemetry.page import page as page_module
 from telemetry.page.actions import scroll
 from telemetry.unittest import tab_test_case
 
@@ skipping 19 matching lines @@
     page = self.CreateAndNavigateToPageFromUnittestDataDir(
         "blank.html",
         page_attributes={"smoothness": {
           "action": "scroll"
           }})
     # Make page bigger than window so it's scrollable.
     self._tab.ExecuteJavaScript("""document.body.style.height =
                               (2 * window.innerHeight + 1) + 'px';""")
 
     self.assertEquals(
-        self._tab.EvaluateJavaScript('document.body.scrollTop'), 0)
+        self._tab.EvaluateJavaScript("""document.documentElement.scrollTop
+                                   || document.body.scrollTop"""), 0)
 
     i = scroll.ScrollAction()
     i.WillRunAction(page, self._tab)
 
     self._tab.ExecuteJavaScript("""
         window.__scrollAction.beginMeasuringHook = function() {
             window.__didBeginMeasuring = true;
         };
         window.__scrollAction.endMeasuringHook = function() {
             window.__didEndMeasuring = true;
         };""")
     i.RunAction(page, self._tab, None)
 
     self.assertTrue(self._tab.EvaluateJavaScript('window.__didBeginMeasuring'))
     self.assertTrue(self._tab.EvaluateJavaScript('window.__didEndMeasuring'))
 
     # Allow for roundoff error in scaled viewport.
     scroll_position = self._tab.EvaluateJavaScript(
-        'document.body.scrollTop + window.innerHeight')
+        """(document.documentElement.scrollTop || document.body.scrollTop)
+        + window.innerHeight""")
     scroll_height = self._tab.EvaluateJavaScript('document.body.scrollHeight')
     difference = scroll_position - scroll_height
     self.assertTrue(abs(difference) <= 1)
 
   def testBoundingClientRect(self):
     self.CreateAndNavigateToPageFromUnittestDataDir('blank.html', {})
     with open(os.path.join(os.path.dirname(__file__), 'scroll.js')) as f:
       js = f.read()
       self._tab.ExecuteJavaScript(js)
 
@@ skipping 20 matching lines @@
         '__ScrollAction_GetBoundingVisibleRect(document.body).width'))
     rect_right = rect_left + rect_width
 
     viewport_height = int(self._tab.EvaluateJavaScript('window.innerHeight'))
     viewport_width = int(self._tab.EvaluateJavaScript('window.innerWidth'))
 
     self.assertTrue(rect_bottom <= viewport_height,
         msg='%s + %s <= %s' % (rect_top, rect_height, viewport_height))
     self.assertTrue(rect_right <= viewport_width,
         msg='%s + %s <= %s' % (rect_left, rect_width, viewport_width))