Hashless hex color quirk for color/background/border only.

According to the quirks mode spec[1], the hashless hex color quirk only
applies to a few properties including color, background-color (not from
short-hand), and various border-color properties.

This aligns the Blink implementation with Gecko and the spec.

The duplicated code and early break is there to avoid regressions in blink
performance tests (there were cases in the CSS and SVG directories that
detected regressions locally).

[1] http://quirks.spec.whatwg.org/#the-hashless-hex-color-quirk

BUG=391343

Review URL: https://codereview.chromium.org/373603004

git-svn-id: svn://svn.chromium.org/blink/trunk@179524 bbb929c8-8fbe-4397-9dbb-9b2b20218538