Provide fallback for scrollingElement in telemetry tests.

document.scrollingElement was added in M44, but apparently the ref build
is currently older than that.  Provide a temporary fallback without
loosing the benefit of https://codereview.chromium.org/1428733002.

CQ_EXTRA_TRYBOTS=tryserver.chromium.perf:linux_perf_bisect;tryserver.chromium.perf:mac_10_10_perf_bisect;tryserver.chromium.perf:win_perf_bisect;tryserver.chromium.perf:android_nexus5_perf_bisect

BUG=549644

Review URL: https://codereview.chromium.org/1425723003

Cr-Commit-Position: refs/heads/master@{#357152}

tools/telemetry/telemetry/internal/actions/action_runner_unittest.py

@@ -229,7 +229,7 @@ class ActionRunnerTest(tab_test_case.TabTestCase):
     action_runner.ScrollPage(direction='right', left_start_ratio=0.9,
                              distance=100)
     self.assertTrue(action_runner.EvaluateJavaScript(
-        'document.scrollingElement.scrollLeft') > 75)
+        '(document.scrollingElement || document.body).scrollLeft') > 75)
 
   @decorators.Disabled('android',   # crbug.com/437065.
                        'chromeos')  # crbug.com/483212.
@@ -253,7 +253,7 @@ class ActionRunnerTest(tab_test_case.TabTestCase):
 
     action_runner.SwipePage(direction='left', left_start_ratio=0.9)
     self.assertTrue(action_runner.EvaluateJavaScript(
-        'document.scrollingElement.scrollLeft') > 75)
+        '(document.scrollingElement || document.body).scrollLeft') > 75)
 
 
 class InteractionTest(unittest.TestCase):

tools/telemetry/telemetry/internal/actions/scroll.js

@@ -20,7 +20,7 @@
       this.speed_ = opt_options.speed;
       this.gesture_source_type_ = opt_options.gesture_source_type;
     } else {
-      this.element_ = document.scrollingElement;
+      this.element_ = document.scrollingElement || document.body;
       this.left_start_ratio_ = 0.5;
       this.top_start_ratio_ = 0.5;
       this.direction_ = 'down';

tools/telemetry/telemetry/internal/actions/scroll.py

@@ -78,7 +78,7 @@ class ScrollAction(page_action.PageAction):
   def RunAction(self, tab):
     if (self._selector is None and self._text is None and
         self._element_function is None):
-      self._element_function = 'document.scrollingElement'
+      self._element_function = '(document.scrollingElement || document.body)'
 
     gesture_source_type = self._synthetic_gesture_source
     if self._use_touch:

tools/telemetry/telemetry/internal/actions/scroll_bounce.py

@@ -38,7 +38,7 @@ class ScrollBounceAction(page_action.PageAction):
 
     if (self._selector is None and self._text is None and
         self._element_function is None):
-      self._element_function = 'document.scrollingElement'
+      self._element_function = '(document.scrollingElement || document.body)'
 
   def WillRunAction(self, tab):
     for js_file in ['gesture_common.js', 'scroll_bounce.js']:

tools/telemetry/telemetry/internal/actions/swipe.py

@@ -56,7 +56,7 @@ class SwipeAction(page_action.PageAction):
   def RunAction(self, tab):
     if (self._selector is None and self._text is None and
         self._element_function is None):
-      self._element_function = 'document.scrollingElement'
+      self._element_function = '(document.scrollingElement || document.body)'
     code = '''
         function(element, info) {
           if (!element) {