Revert 153291 - Fixes crash introduced @ 153047 (you can hit crash by maximizing a

Revert 153291 - Fixes crash introduced @ 153047 (you can hit crash by maximizing a
window). The cross fade code deletes the layer when the animation
finishes. The newly added code was accessing members after the
animation finished and the animator was deleted, resulting in the
crash. Since I'm sure this will come up more in the future I've
restructured the code to allow for deletion when calling out like
this.

The cross fade test exercises this code path now, but I'll see about a
more focused tests shortly.

BUG=129033
TEST=covered by tests.
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Review URL: https://chromiumcodereview.appspot.com/10874064

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Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=153312