Add a pixel-by-pixel comparison tests as discussed before.

1. The test uses a video with only 2 different frames. The first frame
of the video is a blue/pink color frame and the rest are a yellow frame
to avoid any possible error because of image compression.

2. The test loads a page, starts playing the video and trigger PiP.
The PiP window is set to a specific size and then a screenshort is
grabbed.

Change-Id: I63e0ede4013dbeee688770cca06ac673ed6003b3
Reviewed-on: https://chromium-review.googlesource.com/1137533
Commit-Queue: Clifford Cheng <cliffordcheng@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582317}
3 files changed