Fix KeyframeAnimationEffect.toString()

After 6a4d32eedc089e0b69b3b6f9201523bdf47d5313, KeyframeAnimationEffect no
longer has a property attribute.

(cherry picked from commit 999b2051963e94204b1924ea443c1079a825ca1d)
Signed-off-by: Douglas Stockwell <dstockwell@chromium.org>
Remove unused AnimationEffect.getValue()

(cherry picked from commit 422dcf68127e9ad37727acbd7b87bb72c178610d)
Signed-off-by: Douglas Stockwell <dstockwell@chromium.org>
AnimationEffect.sample() should not be public

(cherry picked from commit cc30dba4611e5b16fc20f1cded79aeaf4502370d)
Signed-off-by: Douglas Stockwell <dstockwell@chromium.org>