Bug 1536218 [wpt PR 15510] - Add one test for "Update the Rendering" …

…section of HTML., a=testonly

Automatic update from web-platform-tests
Add one test for "Update the Rendering" section of HTML. (#15510)

I'm hoping to write a bunch of tests for this section, as part of the
investigation of w3ctag/design-reviews#72, and this is the first one.
It tests that request animation frame callbacks happen in the correct
order across multiple documents.

Gecko, Chromium, and WebKit all fail in different (and nondeterministic)
ways, although I've seen occasional passes.
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wpt-commits: 9e96f63ccd0a6e2f5f6511ff1aa8aaaa708b494f
wpt-pr: 15510

UltraBlame original commit: 42f4ccf2ea71530e3bbc66c964504c2ee6ef229f