Move UA style rulesets for <datalist> and input[type=color][list] to html.css

Now all platforms suppor them by default. We don't need to use
RenderTheme::extraDefaultStyleSheet.

BUG=none
TEST=none; no behavior changes.

Review URL: https://codereview.chromium.org/174833002

git-svn-id: svn://svn.chromium.org/blink/trunk@167745 bbb929c8-8fbe-4397-9dbb-9b2b20218538