The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b4bf5e78fabe368cf4005dcb4b3adc19107afab5

commit b4bf5e78fabe368cf4005dcb4b3adc19107afab5
Author: rune <rune@opera.com>
Date: Tue May 03 21:58:16 2016

Make sure computed style is up-to-date for custom properties.

For custom properties, we didn't call updateLayoutTreeForNode which
meant the computed style object might return out-of-date values for
custom properties.

Did some cleanup in getPropertyCSSValue for known properties.

R=shans@chromium.org
BUG= 608690 

Review-Url: https://codereview.chromium.org/1945623002
Cr-Commit-Position: refs/heads/master@{#391368}

[modify] https://crrev.com/b4bf5e78fabe368cf4005dcb4b3adc19107afab5/third_party/WebKit/LayoutTests/fast/css/variables/computed-style.html
[modify] https://crrev.com/b4bf5e78fabe368cf4005dcb4b3adc19107afab5/third_party/WebKit/Source/core/css/CSSComputedStyleDeclaration.cpp