Use neutralKeyframe sentinal instead of '' for interpolation-test.js tests

Use neutralKeyframe sentinal instead of '' for interpolation-test.js tests

This patch updates the animation interpolation and composition test helper
to provide a neutralKeyframe sentinal value for animating to/from a neutral
keyframe.
Previously an empty string was used which acted as a neutral keyframe by
virtue of failing to parse as a value. This refactor makes it more explicit
when neutral keyframes are being tested.

BUG=437696
Committed: https://crrev.com/48e82d85516e01b1fa51c490337c2d55450873e4
Cr-Commit-Position: refs/heads/master@{#386922}

[alancutter (OOO until 2018), 2016-04-13 02:35:19]

alancutter@chromium.org changed reviewers:
+ ericwilligers@chromium.org

[alancutter (OOO until 2018), 2016-04-13 02:35:24]

The CQ bit was checked by alancutter@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-04-13 02:35:45]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1881333002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1881333002/1

[commit-bot: I haz the power, 2016-04-13 03:21:09]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-04-13 03:21:10]

Dry run: Try jobs failed on following builders:
  linux_chromium_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Eric Willigers, 2016-04-13 04:08:09]

lgtm

[alancutter (OOO until 2018), 2016-04-13 05:25:48]

The CQ bit was checked by alancutter@chromium.org

[alancutter (OOO until 2018), 2016-04-13 05:25:49]

The patchset sent to the CQ was uploaded after l-g-t-m from
ericwilligers@chromium.org
Link to the patchset: https://codereview.chromium.org/1881333002/#ps20001
(title: "Fix composition test code")

[commit-bot: I haz the power, 2016-04-13 05:26:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1881333002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1881333002/20001

[commit-bot: I haz the power, 2016-04-13 06:25:48]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-04-13 06:27:05]

Description was changed from

==========
Use neutralKeyframe sentinal instead of '' for interpolation-test.js tests

This patch updates the animation interpolation and composition test helper
to provide a neutralKeyframe sentinal value for animating to/from a neutral
keyframe.
Previously an empty string was used which acted as a neutral keyframe by
virtue of failing to parse as a value. This refactor makes it more explicit
when neutral keyframes are being tested.

BUG=437696
==========

to

==========
Use neutralKeyframe sentinal instead of '' for interpolation-test.js tests

This patch updates the animation interpolation and composition test helper
to provide a neutralKeyframe sentinal value for animating to/from a neutral
keyframe.
Previously an empty string was used which acted as a neutral keyframe by
virtue of failing to parse as a value. This refactor makes it more explicit
when neutral keyframes are being tested.

BUG=437696

Committed: https://crrev.com/48e82d85516e01b1fa51c490337c2d55450873e4
Cr-Commit-Position: refs/heads/master@{#386922}
==========

[commit-bot: I haz the power, 2016-04-13 06:27:06]

Patchset 2 (id:??) landed as
https://crrev.com/48e82d85516e01b1fa51c490337c2d55450873e4
Cr-Commit-Position: refs/heads/master@{#386922}