Clamp the presentation time to a usable range

[chromium-wpt-export-bot]

If the time container is seeked to a large enough value, we will end up
truncating it to SMILTime::Latest(), which is the largest value that
isn't one of the two special values ("indefinite" and "unresolved").
When trying to derive other values from this value - like if we have an
interval begin at it - we can end up in a loop since any the result of
any additions will yield the same value, leading to the element being
rescheduled at the same point in time, hanging UpdateIntervals().
This mechanism can also be used to implement the "once" animation-policy
in a slightly nicer way. This will be done as a follow-up.

Bug: 1039886
Change-Id: If13d7d7d3c44c4f586d15852eb05105879f44918
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2030885
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#737260}

[wpt-pr-bot]

The review process for this patch is being conducted in the Chromium project.

[stephenmcgruer]

The Firefox runs in TaskCluster failed due to #21529.

However, weirdly, neither Chrome nor Safari appear to have seen this test when looking at the change. Safari reports not supporting them:

ERROR Unsupported test type crashtest for product safari

But Chrome just reports no affected tests?

 0:15.17 INFO Identified 0 affected tests
...
 0:37.97 INFO Running crashtest tests
 0:37.97 INFO No crashtest tests to run

[stephenmcgruer]

Figured it out; #21531 should fix the logic to detect when crashtests are changed and run them