GitLab

- Move getImageData-cpu perf test to rendering benchmark
- Remove repeated-draw and repeated-getImageData tests
- Replace usages of Math.random with a counter to force different fill
color for each frame, to keep the tests simple and reduce dependency

Bug: 1077148
Change-Id: Ib7caed70f6a86122c74cee6045179162b3448874
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2316454Reviewed-by: John Chen <johnchen@chromium.org>
Reviewed-by: Juanmi Huertas <juanmihd@chromium.org>
Reviewed-by: Yi Xu <yiyix@chromium.org>
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Commit-Queue: Teresa Kang <teresakang@google.com>
Cr-Commit-Position: refs/heads/master@{#792791}