Bug 1464568 - Set the shadow base transform for animation explicitly even if the transform value hasn't changed. r=kats

That's because the shadow base transform value might have been changed by APZC.

The test case in this patch fail without this fix on non-WebRender and the test
case is skipped on WebRender since the bug should never happen on WebRender
because WebRender manages animation transform value and APZ transform value
separately.

MozReview-Commit-ID: Itgh0QL1su6

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extra : rebase_source : c6f498947ce0be81bfd89f8190f4676f00aa6355