Fixed positioned element with relative percentage positioned parent is wrongly placed

Fixed positioned element with relative percentage positioned parent is wrongly placed

The usage of Length::value() is causing a bug as 25% was translated to 25px,
which is wrong.
Use valueForLength() instead in order to get the accurate value.

Modified current test to add some examples using percentages.

BUG=31286, 425991
TEST=fast/css/css-properties-position-relative-as-parent-fixed.html

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185274

[Manuel Rego, 2014-11-12 23:20:46]

rego@igalia.com changed reviewers:
+ eseidel@chromium.org, jchaffraix@chromium.org, leviw@chromium.org

[leviw_travelin_and_unemployed, 2014-11-12 23:29:59]

LGTM. Gross...

[Manuel Rego, 2014-11-13 06:08:15]

The CQ bit was checked by rego@igalia.com

[commit-bot: I haz the power, 2014-11-13 06:08:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/720003002/1

[commit-bot: I haz the power, 2014-11-13 07:20:34]

Committed patchset #1 (id:1) as 185274