This patch removes ElementAnimations and replaces all references to
ElementAnimations with references to CommonElementAnimationData.
We don't bother to rename variables like 'ea' or methods like
GetElementAnimations to correspond with the data type
(CommonElementAnimationData) since CommonElementAnimationData will soon be
renamed in bug 1010067 and we'll rename these things then.
The ElementAnimationsPropertyDtor function is renamed and merged in a subsequent
patch in this series.