Adding support for diagonal scrolling to telemetry.

tools/perf/page_sets/tough_pinch_zoom_diagonal_scrolling_cases.py

+# Copyright 2015 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.
+from telemetry.page import page as page_module
+from telemetry.page import page_set as page_set_module
+
+
+class ToughPinchZoomDiagonalScrollingCasesPage(page_module.Page):

[jdduke (slow), 2015/02/26 20:34:12]

I wonder if we want to tweak the name here. It almost sounds like we're testing
pinch zoom while diagonal scrolling, or both pinch zoom then diagonal scrolling,
but it's really just testing diagonal scrolling after we're already zoomed in.

Maybe ToughZoomedInDiagonalScrollingCases or
TouchPinchZoomedDiagonalScrollingCases?

[cblume, 2015/02/26 21:33:07]

I agree with you. I'm not a fan of this name and struggled to find something
that clearly conveyed intention. Maybe ToughScrollingCasesWhileZoomedIn? But
many of these end in "Cases" so that would break the mold. However, I don't
think that mold holds much weight.

[jdduke (slow), 2015/02/26 21:42:52]

ToughScrollingWhileZoomedInCases or TouchZoomedInScrollingCases both seem fine.

+
+  def __init__(self, url, page_set):
+    super(ToughPinchZoomDiagonalScrollingCasesPage, self).__init__(
+        url=url,
+        page_set=page_set)
+
+  def RunPageInteractions(self, action_runner):
+    # First, zoom into the page
+    action_runner.PinchPage(
+        scale_factor=20.0,
+        speed_in_pixels_per_second=10000)
+        # 20.0 was chosen because at the time it was close to the maximum.
+        # The more zoomed in, the more noticable the tile rasterization.
+        #
+        # 10,000 was chosen to complete this pre-step quickly.
+
+    # Then start measurements
+    interaction = action_runner.BeginGestureInteraction(
+        'ScrollAction', is_smooth=True)
+    # And begin the diagonal scroll
+    action_runner.ScrollPage(
+        direction='downright',
+        speed_in_pixels_per_second=10000)
+        # 10,000 was chosen because it is fast enough to completely stress the
+        # rasterization (on a Nexus 5) without saturating results.
+    interaction.End()
+
+
+class ToughPinchZoomDiagonalScrollingCasesPageSet(page_set_module.PageSet):
+  """
+  Description: A collection of difficult scrolling tests
+  """
+
+  def __init__(self):
+    super(ToughPinchZoomDiagonalScrollingCasesPageSet, self).__init__(
+        user_agent_type='desktop',
+        archive_data_file='data/tough_pinch_zoom_cases.json',
+        bucket=page_set_module.PARTNER_BUCKET)
+
+    urls_list = [
+        'file://tough_scrolling_cases/background_fixed.html',

[jdduke (slow), 2015/02/26 01:05:35]

I wonder if we want all of these? Not sure, would have to look at the content.

[cblume, 2015/02/26 20:22:00]

We might not want all of these. I copied the list from the
tough_scrolling_cases, figuring both were stressing the scrolling. It seemed
like a fair enough place to start and perhaps some tests which looked
unimportant were actually beneficial in a way I didn't realize.

I've run the test several times and the general ordering of
mean_pixels_approximated for the page sets seem consistent. What I mean by that
is background_fixed.html seems to consistently be the worst offender.
cust_scrollbar.html and fixed_stacking.html both seem to perform well.

We can set the scrolling speeds just right to stress rasterization. If something
has 100% mean_pixels_approximated then we won't know if things have gotten
worse. Likewise, if it is 0% we won't know if things have gotten better. So I
was aiming to get the tests ~50%.

I was testing on a Nexus 5. background_fixed.html (the worst offender) is the
only one that is near 50% at this scroll speed. The next most visible is
iframe_scrolls.html at ~25%, then fixed_nonstacking.html at ~18%. As you can
see, it diverts away from 50% pretty quickly.

Perhaps I should alter the scroll speed to maximize the quantity near 50% and
then remove the other tests which aren't close?

[jdduke (slow), 2015/02/26 20:34:12]

I think the speed you have is fine, let's pick the worst 4 or so and add a
comment before the urls_list saying why, e.g.,

# Why: Exhibit >20% checkerboarding at high velocities

or something like that.

[cblume, 2015/02/26 21:33:07]

Good idea. I'll do that.

+        'file://tough_scrolling_cases/cust_scrollbar.html',
+        'file://tough_scrolling_cases/div_scrolls.html',
+        'file://tough_scrolling_cases/fixed_nonstacking.html',
+        'file://tough_scrolling_cases/fixed_stacking.html',
+        'file://tough_scrolling_cases/iframe_scrolls.html',
+        'file://tough_scrolling_cases/simple.html',
+        'file://tough_scrolling_cases/wheel_body_prevdefault.html',
+        'file://tough_scrolling_cases/wheel_div_prevdefault.html'
+    ]
+
+    for url in urls_list:
+      self.AddUserStory(ToughPinchZoomDiagonalScrollingCasesPage(url, self))