Fix computation of scroll amount in scroll actions.

telemetry/telemetry/internal/actions/key_event_unittest.py

 # Copyright 2016 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 time
 
 from telemetry.internal.actions import key_event
+from telemetry.internal.actions import utils
 from telemetry.testing import tab_test_case
 
 
 class KeyPressActionTest(tab_test_case.TabTestCase):
 
   @property
   def _scroll_position(self):
     return self._tab.EvaluateJavaScript(
         'document.documentElement.scrollTop || document.body.scrollTop')
 
   @property
   def _window_height(self):
-    return self._tab.EvaluateJavaScript('window.innerHeight')
+    return self._tab.EvaluateJavaScript('__GestureCommon_GetWindowHeight()')
 
   def _PressKey(self, key):
     action = key_event.KeyPressAction(key)
     action.WillRunAction(self._tab)
     action.RunAction(self._tab)
 
   def setUp(self):
     tab_test_case.TabTestCase.setUp(self)
     self.Navigate('blank.html')
+    utils.InjectJavaScript(self._tab, 'gesture_common.js')
 
   def testPressEndAndHome(self):
     # Make page taller than the window so it's scrollable.
-    self._tab.ExecuteJavaScript(
-        'document.body.style.height = (3 * window.innerHeight + 1) + "px";')
+    self._tab.ExecuteJavaScript('document.body.style.height ='
+        '(3 * __GestureCommon_GetWindowHeight() + 1) + "px";')
 
     # Check that the browser is currently showing the top of the page and that
     # the page has non-trivial height.
     self.assertEquals(0, self._scroll_position)
     self.assertLess(50, self._window_height)
 
     self._PressKey('End')
 
     # Scroll happens *after* key press returns, so we need to wait a little.
     time.sleep(1)
@@ skipping 29 matching lines @@
     self._PressKey('Return')
 
     # Check that the contents of the textarea is correct.
     self.assertEquals('Hello,\nWorld!',
                       self._tab.EvaluateJavaScript(
                           'document.querySelector("textarea").value'))
 
   def testPressUnknownKey(self):
     with self.assertRaises(ValueError):
       self._PressKey('UnknownKeyName')