Simplify animation/transition parsing slightly

Simplify animation/transition parsing slightly

This patch simplifies parsing CSS animations and transitions slightly by
making us only return CSSValueLists from the parser, including when we
only have a single value in the list. This was probably done differently
in the past (with single values not being wrapped in a CSSValueList) as
premature optimisation, which adds needless complexity to the code. Note
this changes the foo.style.getPropertyCSSValue output slightly.

I've also made BisonCSSParser::parseAnimationTimingFunctionValue return
a single (non-valuelist-wrapped) CSSValue which isn't initial or inherit
to better match the intention of the callers.

R=alancutter,dstockwell

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=175153

[dstockwell, 2014-05-29 22:17:38]

lgtm

[Timothy Loh, 2014-05-30 03:50:04]

The CQ bit was checked by timloh@chromium.org

[commit-bot: I haz the power, 2014-05-30 03:53:19]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/timloh@chromium.org/293113007/40001

[Paweł Hajdan Jr., 2014-05-30 16:23:50]

The CQ bit was unchecked by phajdan.jr@chromium.org

[Paweł Hajdan Jr., 2014-05-30 16:28:51]

The CQ bit was checked by phajdan.jr@chromium.org

[commit-bot: I haz the power, 2014-05-30 16:31:02]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/timloh@chromium.org/293113007/40001

[commit-bot: I haz the power, 2014-05-30 17:12:53]

Change committed as 175153