Add tests for different UpdateRect methods as they are no longer trivial This change will enable providing useful update rects after scaling is done. Bug: webrtc:11058 Change-Id: I2311dbbbb5eca5cfaf845306674e6890050f80c6 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/159820 Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org> Reviewed-by: Niels Moller <nisse@webrtc.org> Reviewed-by: Stefan Holmer <stefan@webrtc.org> Cr-Commit-Position: refs/heads/master@{#29835}