Add base LayoutStyle parameter to createAnimatableValueSnapshot()

Add base LayoutStyle parameter to createAnimatableValueSnapshot()

This patch has no behavioural changes.
This change allows for an arbitrary LayoutStyle to be used as the context style when
snapshotting AnimatableValues.
This is in preparation for using StringKeyframes in CSS Animations (https://codereview.chromium.org/948583003).
CSS Animations that start on the first frame in style resolve still have the current
LayoutStyle in a temporary variable instead of in the element. This needs to be passed
though to createAnimatableValueSnapshot() to ensure the AnimatableValues are resolved
correctly for dependent values like inherit or 20em.

BUG=361948
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=191846

[alancutter (OOO until 2018), 2015-03-12 09:22:37]

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

[dstockwell, 2015-03-13 02:43:32]

lgtm

[alancutter (OOO until 2018), 2015-03-13 02:48:17]

The CQ bit was checked by alancutter@chromium.org

[commit-bot: I haz the power, 2015-03-13 02:48:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/999963003/1

[commit-bot: I haz the power, 2015-03-13 03:41:55]

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

[commit-bot: I haz the power, 2015-03-13 03:41:56]

Try jobs failed on following builders:
  mac_blink_rel on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/mac_blink_rel/builds/47201)

[alancutter (OOO until 2018), 2015-03-13 08:21:01]

The CQ bit was checked by alancutter@chromium.org

[alancutter (OOO until 2018), 2015-03-13 08:21:01]

The patchset sent to the CQ was uploaded after l-g-t-m from
dstockwell@chromium.org
Link to the patchset: https://codereview.chromium.org/999963003/#ps20001 (title:
"Rebase")

[commit-bot: I haz the power, 2015-03-13 08:21:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/999963003/20001

[commit-bot: I haz the power, 2015-03-13 09:15:49]

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

[commit-bot: I haz the power, 2015-03-13 09:15:50]

Try jobs failed on following builders:
  linux_chromium_gn_rel on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/linux_chromium_gn_rel/bu...)

[alancutter (OOO until 2018), 2015-03-13 12:37:15]

The CQ bit was checked by alancutter@chromium.org

[commit-bot: I haz the power, 2015-03-13 12:37:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/999963003/20001

[alancutter (OOO until 2018), 2015-03-13 12:49:41]

The CQ bit was checked by alancutter@chromium.org

[alancutter (OOO until 2018), 2015-03-13 12:49:41]

The patchset sent to the CQ was uploaded after l-g-t-m from
dstockwell@chromium.org
Link to the patchset: https://codereview.chromium.org/999963003/#ps40001 (title:
"Missing include")

[commit-bot: I haz the power, 2015-03-13 12:49:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/999963003/40001

[commit-bot: I haz the power, 2015-03-13 15:34:34]

Committed patchset #3 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=191846