Fix seeking and scaled duration behavior

The animation scaled was not being factored in early enough in the
activity lifecycle. Also, setCurrentPlaytTime() was not accounting for
the scaled duration correctly. Finally, added setCurrentFraction() as
a more general-purpose seeking facility.

Issue #18222006 Animator duration scale ignored in some situations
Issue #17951668 add ability to seek fraction, not just time

Change-Id: Idad401f5ff5026d7046c36eee09d78a4793215dc