Disable 4 and 8 digit hex CSS colors

New compat concerns have been raised with 4 and 8 digit HEX color
values in CSS.  In particular, a targetSdk quirk needs to be added
for Android WebView to avoid breaking Android apps.

Demote this feature to "experimental" status until an owner can be found.

BUG=618518, 76362

Review-Url: https://codereview.chromium.org/2047413003
Cr-Commit-Position: refs/heads/master@{#398789}
(cherry picked from commit b7bc5783027ae86ff6eb6912d0a6112cda6a8814)

Review URL: https://codereview.chromium.org/2086433003 .

Cr-Commit-Position: refs/branch-heads/2743@{#413}
Cr-Branched-From: 2b3ae3b8090361f8af5a611712fc1a5ab2de53cb-refs/heads/master@{#394939}
2 files changed