Preserve shape-box order in non-computed values

When a shape and box are supplied for a shape-property, the order they
are input should be preserved in output from the CSSOM. This patch parses
the shape and box values as a CSSValueList to preserve that ordering,
and removes the need for BasicShapes to have a sizing box.

BUG=322165

Review URL: https://codereview.chromium.org/144143005

git-svn-id: svn://svn.chromium.org/blink/trunk@168477 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Disable some compositing state asserts seen on Mac builds

Test scenarios:
http://www.rbyers.net/eventTest.html - scrolling the page or div (has a wheel handler but doesn't call preventDefault)
Loading https://twitter.com/pwnall

BUG=343132

Review URL: https://codereview.chromium.org/180803012

git-svn-id: svn://svn.chromium.org/blink/trunk@168478 bbb929c8-8fbe-4397-9dbb-9b2b20218538