Update telemetry tests to be agnostic to ScrollTopLeftInterop mode

tools/telemetry/telemetry/internal/actions/swipe.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.
 
 import os
 
 from telemetry.internal.actions import page_action
 
 
 class SwipeAction(page_action.PageAction):
@@ skipping 38 matching lines @@
 
     done_callback = 'function() { window.__swipeActionDone = true; }'
     tab.ExecuteJavaScript("""
         window.__swipeActionDone = false;
         window.__swipeAction = new __SwipeAction(%s);"""
         % (done_callback))
 
   def RunAction(self, tab):
     if (self._selector is None and self._text is None and
         self._element_function is None):
-      self._element_function = 'document.body'
+      self._element_function = 'document.scrollingElement'
     code = '''
         function(element, info) {
           if (!element) {
             throw Error('Cannot find element: ' + info);
           }
           window.__swipeAction.start({
             element: element,
             left_start_ratio: %s,
             top_start_ratio: %s,
             direction: '%s',
             distance: %s,
             speed: %s
           });
         }''' % (self._left_start_ratio,
                 self._top_start_ratio,
                 self._direction,
                 self._distance,
                 self._speed)
     page_action.EvaluateCallbackWithElement(
         tab, code, selector=self._selector, text=self._text,
         element_function=self._element_function)
     tab.WaitForJavaScriptExpression('window.__swipeActionDone', 60)