[tools/perf] Remove smoothness.tough_animated_image_cases

tools/perf/page_sets/tough_animated_image_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 import story
-
-class ToughAnimatedImageCasesPage(page_module.Page):
-
-  def __init__(self, url, page_set):
-    super(ToughAnimatedImageCasesPage, self).__init__(
-        url=url, page_set=page_set)
-
-  def RunPageInteractions(self, action_runner):
-    with action_runner.CreateInteraction('ToughAnimatedImage'):
-      action_runner.Wait(10)
-
-class ToughAnimatedImageCasesPageSet(story.StorySet):
-
-  """
-  Description: A collection of difficult animated image tests
-  """
-
-  def __init__(self):
-    super(ToughAnimatedImageCasesPageSet, self).__init__()
-
-    urls_list = [
-      'file://tough_animated_image_cases/gifs.html'
-    ]
-
-    for url in urls_list:
-      self.AddStory(ToughAnimatedImageCasesPage(url, self))