Adding telemetry test for page scroll using scrollbar drag.

tools/perf/page_sets/top_25_smooth.py

Index: tools/perf/page_sets/top_25_smooth.py
diff --git a/tools/perf/page_sets/top_25_smooth.py b/tools/perf/page_sets/top_25_smooth.py
index b19a0bf8b7d5e372870fd61229fd1faa6ae3f408..ca055f738ac0f4de78f6b583bc1ee919356a7422 100644
--- a/tools/perf/page_sets/top_25_smooth.py
+++ b/tools/perf/page_sets/top_25_smooth.py
@@ -53,6 +53,49 @@ class GmailSmoothPage(top_pages.GmailPage):
     interaction.End()
 
 
+class GmailMouseScrollPage(top_pages.GmailPage):
+
+  """ Why: productivity, top google properties """
+
+  def RunPageInteractions(self, action_runner):
+    action_runner.ExecuteJavaScript('''
+        gmonkey.load('2.0', function(api) {
+          window.__scrollableElementForTelemetry = api.getScrollableElement();
+        });''')
+    action_runner.WaitForJavaScriptCondition(
+        'window.__scrollableElementForTelemetry != null')
+    scrollbar_x, start_y, end_y = self.CalculateScrollBarRatios(action_runner)
+
+    interaction = action_runner.BeginGestureInteraction(
+        'DragAction', is_smooth=True)
+    action_runner.DragPage(left_start_ratio=scrollbar_x,
+        top_start_ratio=start_y, left_end_ratio=scrollbar_x,
+        top_end_ratio=end_y, speed_in_pixels_per_second=100,
+        element_function='window.__scrollableElementForTelemetry')
+    interaction.End()
+
+  def CanRunOnBrowser(self, browser_info):
+    return (browser_info._browser._platform_backend.platform.GetOSName() !=
+        'android')
+
+  def CalculateScrollBarRatios(self, action_runner):

[Sami, 2015/03/06 15:02:04]

nit: Start this name with an underscore since it's an internal helper.

[ssid, 2015/03/06 16:45:55]

Done.

+    display_height = float(action_runner.EvaluateJavaScript(

[Sami, 2015/03/06 15:02:04]

I think you want .clientHeight here (and also rename display_height to something
like viewport_height).

[ssid, 2015/03/06 16:45:55]

Done.

+        'window.__scrollableElementForTelemetry.offsetHeight'))
+    page_height = float(action_runner.EvaluateJavaScript(

[Sami, 2015/03/06 15:02:04]

nit: content_height?

[ssid, 2015/03/06 16:45:55]

Done.

+        'window.__scrollableElementForTelemetry.scrollHeight'))
+    display_width = float(action_runner.EvaluateJavaScript(
+        'window.__scrollableElementForTelemetry.offsetWidth'))
+    scrollbar_width = float(action_runner.EvaluateJavaScript('''

[Sami, 2015/03/06 15:02:04]

Add a comment here that this only works if the scrollable element has no border
or padding.

[ssid, 2015/03/06 16:45:55]

Done.

+        window.__scrollableElementForTelemetry.offsetWidth -
+        window.__scrollableElementForTelemetry.scrollWidth'''))
+
+    scrollbar_start_mid_y = display_height / (2 * page_height)
+    scrollbar_end_mid_y = 1 - scrollbar_start_mid_y
+    scrollbar_mid_x_offset = scrollbar_width / (2 * display_width)
+    scrollbar_mid_x = 1 - scrollbar_mid_x_offset
+    return scrollbar_mid_x, scrollbar_start_mid_y, scrollbar_end_mid_y
+
+
 class GoogleCalendarSmoothPage(top_pages.GoogleCalendarPage):
 
   """ Why: productivity, top google properties """
@@ -118,6 +161,7 @@ class Top25SmoothPageSet(page_set_module.PageSet):
     self.AddUserStory(_CreatePageClassWithSmoothInteractions(
         top_pages.GoogleWebSearchPage)(self))
     self.AddUserStory(GmailSmoothPage(self))
+    self.AddUserStory(GmailMouseScrollPage(self))
     self.AddUserStory(GoogleCalendarSmoothPage(self))
     self.AddUserStory(_CreatePageClassWithSmoothInteractions(
         top_pages.GoogleImageSearchPage)(self))