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This adds
1.) cropping test case (crop 360p frame 480p frame), and
2.) cropping+scaling test case (crop 360p frame 480p frame and scale
    the image to 270p)

This adds visible rectangle element to media::test::Image.

Bug: 1034415
Test: IPtest on atlas
Change-Id: Ie16d413d0e81029b98209a7eec4eeac6c4691639
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1974303
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: David Staessens <dstaessens@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728839}