GitLab

Move tough_scheduling_cases into the rendering folder and refactor
classes to inherit from RenderingStory

Bug: 849392
Change-Id: I247f9aff4fde03cda7ea479a9dcf88c04960c749
Reviewed-on: https://chromium-review.googlesource.com/1089459Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Amy Qiu <amyqiu@google.com>
Cr-Commit-Position: refs/heads/master@{#565290}