GitLab

Clean up PrintRenderFrameHelperTest.

- Deduplicate ClickMouseButton() code.
- Add an accessor to print_render_thread().
- Mark function level constants as static.
- Use std::make_unique() and default ctor/dtors.

Change-Id: I545d69935324b9e8b7943132dc90f2c1334b9025
Reviewed-on: https://chromium-review.googlesource.com/c/1370468Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615621}