Avoid conditional Animation prefinalizers.

Recast the conditionally-eager finalization of Animation objects - only
needed if the Animation object has a CompositorAnimationPlayer attached -
wrapping instead the player object inside an eagerly-finalized object.

By doing so, we remove the need to support explicit prefinalizer
registration.

R=haraken
BUG=673645

Review-Url: https://codereview.chromium.org/2570503002
Cr-Commit-Position: refs/heads/master@{#438089}
2 files changed