Animation: Fix bug in timing in compositor

Animation: Fix bug in timing in compositor

An edge case around direction and playback rate is calculating the time
incorrectly. In particular, when the playback rate is negative and the
direction is set to AlternateReverse, the resulting iteration times
calculated are incorrect. This change brings the compositor in line
with the Web Animation Spec to calculate the iteration time.

Reference for calculations:
http://dev.w3.org/fxtf/web-animations/#core-animation-node-calculations

BUG=398330
Committed: https://crrev.com/35099b0441b16ba4ed5f3a331f77bd59f6610926
Cr-Commit-Position: refs/heads/master@{#294708}

[samli, 2014-09-12 21:03:28]

samli@chromium.org changed reviewers:
+ ajuma@chromium.org

[samli, 2014-09-12 21:03:29]

PTAL

[ajuma, 2014-09-12 22:33:11]

On 2014/09/12 21:03:29, samli wrote:
> PTAL

Nice, lgtm.

[samli, 2014-09-12 23:07:42]

The CQ bit was checked by samli@chromium.org

[commit-bot: I haz the power, 2014-09-12 23:12:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/565353003/1

[commit-bot: I haz the power, 2014-09-13 00:51:36]

Committed patchset #1 (id:1) as 0b577cdfccffebec7558263344afc43afbe09171

[commit-bot: I haz the power, 2014-09-13 00:54:46]

Patchset 1 (id:??) landed as
https://crrev.com/35099b0441b16ba4ed5f3a331f77bd59f6610926
Cr-Commit-Position: refs/heads/master@{#294708}