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There are crashes during destruction where |side_data_size_| == 0
but |side_data_| contains an invalid pointer. Adding a CHECK for this
in the destructor to hopefully get better data to help isolate the
real problem.

BUG=794740
TEST=media_unittests still pass

Change-Id: Id1633395c544b66ef632445d475a40e57a8aa1b4
Reviewed-on: https://chromium-review.googlesource.com/1185961
Commit-Queue: John Rummell <jrummell@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585354}