Bug 1478643 - Apply change hints for transform animation in the case where the current transform style is 'none' and no change hint produced in AddLayerChangesForAnimation. r=birtles

The applying change hints are the same as what we apply for transform style
changed from something to 'none'.

All test cases pass with this fix fail without the fix.

MozReview-Commit-ID: 7HStU26lRPq

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extra : rebase_source : 701361d477ab7954ab15fde75fd40d98724e47b3