service worker: Add tests for canvas tainting from a video with range requests.

This tests that a canvas is tainted when the video had multiple responses
from a service worker, if any of the responses were opaque.

Bug: 780435
Change-Id: Ifef394c87921cb646b1728a9079908264673fdd4
Reviewed-on: https://chromium-review.googlesource.com/897165
Reviewed-by: Tsuyoshi Horo <horo@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533869}
6 files changed