Reenabling an old unit test for scrolling.

tools/telemetry/telemetry/page/actions/scroll_unittest.py

 # Copyright 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 import decorators
 from telemetry.page.actions import scroll
 from telemetry.unittest_util import tab_test_case
 
 
 class ScrollActionTest(tab_test_case.TabTestCase):
-  @decorators.Disabled  # Disabled due to flakiness: crbug.com/330544
   def testScrollAction(self):
     self.Navigate('blank.html')
 
     # 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.documentElement.scrollTop
                                    || document.body.scrollTop"""), 0)
 
     i = scroll.ScrollAction()
     i.WillRunAction(self._tab)
 
     self._tab.ExecuteJavaScript("""
         window.__scrollAction.beginMeasuringHook = function() {
             window.__didBeginMeasuring = true;
         };
         window.__scrollAction.endMeasuringHook = function() {
             window.__didEndMeasuring = true;
         };""")
     i.RunAction(self._tab)
 
     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.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,
-                    msg='scroll_position=%d; scroll_height=%d' %
-                            (scroll_position, scroll_height))
+        """(document.documentElement.scrollTop || document.body.scrollTop)""")

[sullivan, 2015/03/05 03:03:58]

Nit: Don't need the triple quotes since this fits on one line now.

+    self.assertTrue(scroll_position != 0,
+                    msg='scroll_position=%d;' % (scroll_position))
 
   def testBoundingClientRect(self):
     self.Navigate('blank.html')
 
     with open(os.path.join(os.path.dirname(__file__),
                            'gesture_common.js')) as f:
       js = f.read()
       self._tab.ExecuteJavaScript(js)
 
     # Verify that the rect returned by getBoundingVisibleRect() in scroll.js is
@@ skipping 27 matching lines @@
     viewport_width = int(self._tab.EvaluateJavaScript('window.innerWidth'))
 
     self.assertTrue(rect_top >= 0,
         msg='%s >= %s' % (rect_top, 0))
     self.assertTrue(rect_left >= 0,
         msg='%s >= %s' % (rect_left, 0))
     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))