GitLab

Move tough_scrolling_cases into the rendering folder and refactor to
inherit from RenderingStory

Bug: 849392
Change-Id: I7edf70dedb6fd74e2741c568cfc5df35a35ecbf1
Reviewed-on: https://chromium-review.googlesource.com/1089038
Commit-Queue: Amy Qiu <amyqiu@google.com>
Reviewed-by: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#565009}