Digging into several crashing tests revealed that committing
transactions is a fallible operation. Propagating those errors led to
exposing many new errors caused by the IDBRequest implementation
assuming that all successful responses contained a structured clone. The
end result is a bunch of new test failures that were previously hidden.
Testing: Existing test coverage is sufficient.
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Signed-off-by: Josh Matthews <josh@joshmatthews.net>
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