MediaRecorder: Upstream some moarrrr web_tests to WPT

This CL moves MediaRecorder-events-and-exceptions.html to the wpt/
folder, and refactors it to use canvas.captureStream() (ISO the
Chrome-specific blink_test_runner.cc thing).

It also fixes partially MediaRecorder-error.html: a new method
drawSomethingOnCanvas() is introduced and called to guarantee
that the canvas produces some captured VideoFrame, kicking the
event(s) generation. This fix is partial because Chrome doesn't
have MediaRecorderErrorEvent, but at least we verify that an
error event is thrown.

Bug: 919951
Change-Id: Ie9d7cfeeb2bf4452f4b5928eb2a7c644778751a7
Reviewed-on: https://chromium-review.googlesource.com/c/1406150
Reviewed-by: Emircan Uysaler <emircan@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622121}
4 files changed